TW202126465A - Layered polyester film and method of manufacturing the same, protective sheet for solar cell, and solar cell module - Google Patents

Abstract

An embodiment of the invention provides a laminated polyester film and a method for producing the same, a protective sheet for solar cells that includes the laminated polyester film, and a solar cell module. The laminated polyester film includes: a biaxially oriented polyester film, produced by stretching an unstretched polyester film in a first direction and in a second direction orthogonal to the first direction along a film surface, and having a small peak temperature of 160 to 210°C derived from a heat setting temperature measured by differential scanning calorimetry; and an undercoat layer, formed by coating a surface of the polyester film stretched in the first direction with a composition for forming an undercoat layer before stretching the polyester film in the second direction, and then stretching the polyester film in the second direction, and having an elastic modulus of 0.7 GPa or more.

Description

Laminated polyester film and its manufacturing method, protective sheet for solar cell and solar cell module

One embodiment of the present invention relates to a laminated polyester film, a method of manufacturing the same, a protective sheet for solar cells, and a solar cell module.

Polyester film is used in many aspects, such as protective films for solar cells, optical films, tracing films, packaging films, magnetic tapes, and insulating tapes. When a polyester film is used for these applications, usually the polyester film is used next to other raw materials in many cases.

For example, a case where a polyester film is used for a protective sheet for solar cells is given as an example. The solar cell module usually has the following structure: sandwiched between a front substrate arranged on the surface side where sunlight is incident and a back protection sheet placed on the opposite side (back side) from the surface where sunlight is incident A solar cell unit of a solar cell element sealed with a sealing material. Moreover, as the sealing material, ethylene-vinyl acetate copolymer (EVA) resin or the like is generally used. That is, when the polyester film is used for solar cell applications, the adhesiveness between the polyester film and the sealing material is required. Furthermore, the environment in which the solar cell module is generally used is an environment that is often exposed to wind and rain, such as outdoors. Therefore, the weather resistance of the solar cell protective sheet is also one of the important issues.

In such an environment (for example, in a humid and hot environment), it is important for the solar cell protective sheet to have the following degree of weather resistance (moist heat stability): the sealing material adjacent to the solar cell protective sheet and the solar cell protective sheet are not Peeling, and when the solar cell protective sheet has a laminated structure, no peeling occurs between the layers in the solar cell protective sheet.

Therefore, various protective sheets for solar cells that aim to improve weather resistance have been proposed. For example, Japanese Patent Laid-Open No. 2014-76632 proposes a laminated film, which includes a polyester film and a coating layer laminated on at least one surface of the polyester film. The coating layer contains an acid-modified polyolefin resin and A basic compound having a boiling point of 200°C or less, and the polyester film contains a compound derived from an acid-modified polyolefin resin contained in the coating layer. The laminated film is formed with a coating layer using a polyolefin resin by an in-line coating method, thereby having excellent adhesiveness and water resistance.

On the other hand, in Japanese Patent Laid-Open No. 2012-189665, a biaxially stretched polyethylene terephthalate film is proposed in which the coating layer is placed in the heat setting process by in-line coating. On the polyethylene terephthalate film treated at 220°C or higher and 230°C or lower. The biaxially stretched polyethylene terephthalate film is used as a polyester film for optical film applications, and can coexist the optical axis accuracy and the thermal dimensional stability of the film.

[The problem to be solved by the invention] However, like the laminated film disclosed in Japanese Patent Laid-Open No. 2014-76632, a laminated polyester film having a layer using a polyolefin resin has adhesiveness with sealing materials such as ethylene-vinyl acetate copolymer (EVA). Good, but the polyester film used as the base material is easily broken by aggregation. As a result, the polyester film may peel off from the sealing material. On the other hand, by increasing the heat fixing temperature and disturbing the molecular alignment, the strength of the polyester film becomes higher, and the resistance to aggregation destruction (resistance to aggregation destruction) improves. However, if the heat fixation temperature is increased, the weather resistance (humid heat stability) of the polyester film tends to decrease. Therefore, the actual situation has not yet provided a laminated polyester film that combines cohesion resistance and weather resistance (humid heat stability).

One embodiment of the present invention is made in view of the above-mentioned situation. The object of one embodiment of the present invention is to provide a laminated polyester film that has cohesion resistance and weather resistance (humid heat stability) and its production A method, a protective sheet for solar cells, and a solar cell module with long-term durability, and achieving this objective is a subject. [Means to solve the problem]

Specific means to solve the problem include the following forms. <1> A laminated polyester film comprising: a biaxially stretched polyester film, by extending the unstretched polyester film in a first direction, and extending along the surface of the film in a second direction orthogonal to the first direction It is produced by stretching in two directions, and the minute peak temperature derived from the heat fixation temperature measured by differential scanning calorimetry is 160°C or more and 210°C or less; and the primer layer is made by stretching in the second direction before The composition for forming an undercoat layer is applied to one surface of a polyester film stretched in the first direction and stretched in the second direction to form the composition, and the elastic modulus is 0.7 GPa or more.

<2> The laminated polyester film according to <1>, in which the primer layer contains an acrylic resin, and the content ratio of the acrylic resin in the resin component contained in the primer layer is 50% by mass or more. <3> The laminated polyester film according to <2>, in which the content ratio of the acrylic resin in the resin component contained in the primer layer is 75% by mass or more. <4> The laminated polyester film as described in <2> or <3>, in which the acrylic resin contained in the primer layer has a styrene skeleton. <5> The laminated polyester film according to any one of <1> to <4>, wherein the elastic modulus of the primer layer is 1.0 GPa or more.

<6> The laminated polyester film according to any one of <1> to <5>, wherein the elastic modulus of the primer layer is 1.3 GPa or more. <7> The laminated polyester film according to any one of <1> to <6>, wherein the micro-peak temperature of the biaxially stretched polyester film is 170° C. or more and 200° C. or less. <8> The laminated polyester film according to any one of <1> to <7>, wherein the micro-peak temperature of the biaxially stretched polyester film is 180°C or more and 190°C or less. <9> The laminated polyester film according to any one of <1> to <8>, in which the primer layer further contains an oxazoline-based crosslinking agent.

<10> A protective sheet for solar cells, comprising: the laminated polyester film according to any one of <1> to <9>, and an acrylic resin containing acrylic resin disposed on the undercoat layer of the laminated polyester film The resin layer. <11> The solar cell protective sheet according to <10>, wherein the resin layer has a structure in which at least two layers are laminated, and the outermost layer farthest from the laminated polyester film contains acrylic resin and polyolefin resin. <12> The solar cell protective sheet as described in <10> or <11>, which has a weather-resistant layer on the side opposite to the side having the primer layer of the laminated polyester film. <13> The solar cell protective sheet according to <12>, wherein the weather-resistant layer has a structure in which at least two layers are laminated, and the weather-resistant layer farthest from the laminated polyester film contains a fluorine-based resin. <14> A solar cell module including the protective sheet for solar cells as described in any one of <10> to <13>.

<15> A method for producing a laminated polyester film, which includes the step of extending the unstretched polyester film in the first direction; The step of stretching one side of the polyester film; the polyester film coated with the primer-forming composition is stretched along the film surface in a second direction orthogonal to the first direction to form an elastic mold The step of heat-fixing the polyester film formed with the primer layer at a temperature of 165°C or higher and 215°C or lower; and the production of a biaxially formed primer layer Stretch the polyester film. [Effects of the invention]

According to an embodiment of the present invention, there is provided a laminated polyester film that combines cohesion resistance and weather resistance (moisture and heat stability), a method of manufacturing the same, a protective sheet for solar cells, and a solar cell module with long-term durability .

＜Laminated polyester film＞ The laminated polyester film includes: a biaxially stretched polyester film (hereinafter, also referred to as a base material as appropriate). The unstretched polyester film is stretched in the first direction and along the surface of the film in the same direction as the first direction. It is produced by stretching in the second orthogonal direction, and the minute peak temperature derived from the heat fixation temperature measured by differential scanning calorimetry is 160°C or more and 210°C or less; Before stretching in two directions, the composition for forming an undercoat layer is applied to one surface of the polyester film stretched in the first direction and stretched in the second direction to form it, and the modulus of elasticity is 0.7 Above GPa. By including the above-mentioned configuration, the laminated polyester film is less likely to cause cohesion failure, and can achieve coexistence of cohesion failure resistance and weather resistance (humid heat stability).

Although the effect of one embodiment of the present invention is not clear, the inventors of the present invention estimated as follows. That is, it is considered that the laminated polyester film contains an undercoating layer having an elastic modulus of 0.7 GPa or more to effectively suppress the cohesive failure of the biaxially stretched polyester film as the base material. Therefore, in the past, by increasing the heat-fixing temperature of the base material, the strength of the base material was increased and the cohesive destruction of the base material was suppressed, but the treatment can be performed at a temperature lower than the heat-fixing temperature of the previous base material. The heat-fixing temperature of the base material contributes to the moisture-heat stability. If the heat-fixing temperature is within a predetermined range, the moisture-heat stability becomes good. On the other hand, if it deviates from the predetermined temperature range, the moisture-heat stability decreases. That is, it can be considered that the laminated polyester film is a biaxially stretched polyester film in which the minute peak temperature derived from the heat fixation temperature measured by differential scanning calorimetry (Differential Scanning Calorimetry, DSC) is 160°C or more and 210°C or less. As a substrate, it can maintain moisture and heat stability. It is considered that in the laminated polyester film, these interactions can make cohesion resistance and weather resistance (moist heat stability) coexist.

[Biaxially stretched polyester film] The laminated polyester film includes the following biaxially stretched polyester film: the unstretched polyester film is stretched in the first direction and stretched along the film surface in the second direction orthogonal to the first direction It is produced, and the minute peak temperature derived from the heat fixation temperature measured by differential scanning calorimetry is 160°C or more and 210°C or less.

(Minute peak temperature) The minute peak temperature derived from the heat fixation temperature measured by differential scanning calorimetry reflects the processing temperature (heat fixation temperature) in the heat fixation step when the laminated polyester film is produced.

When the biaxially stretched polyester film has a small peak temperature derived from the heat fixation temperature measured by differential scanning calorimetry (DSC) of 160°C or higher, the biaxially stretched polyester film has high crystallinity and is made into a laminated polymer film. The weather resistance in the case of an ester film is excellent. In addition, when the minute peak temperature is 210° C. or lower, the biaxially stretched polyester film is a polyester film with well-aligned molecules, and therefore, when it is made into a laminated polyester film, it has excellent weather resistance.

The biaxially stretched polyester film has a micro-peak temperature derived from the heat setting temperature measured by DSC, preferably 170°C or higher and 200°C or lower, more preferably 180°C or higher and 190°C or lower. When the micro peak temperature is in the above range, the weather resistance of the laminated polyester film will be more excellent when the laminated polyester film is formed.

The small peak temperature is measured by the following method. The small peak temperature is measured in accordance with JIS K7122-1987 (refer to the 1999 edition of the JIS manual) using a differential scanning calorimetry device "Robot DSC-RDC220" manufactured by Seiko Instruments Inc. Data analysis uses Disk Session "SSC/5200". Specifically, 5 mg of a biaxially stretched polyester film was weighed in a sample pan, and the temperature was increased at a temperature increase rate of 20°C/min from 25°C to 300°C, and the minute peak temperature was measured. The minute peak temperature is determined by reading the temperature of the minute endothermic peak before the crystal melting peak (the temperature side lower than the crystal melting peak) in the differential scanning calorimetry chart obtained by the measurement. When it is difficult to observe a minute endothermic peak, the vicinity of the crystal melting peak in the graph is enlarged to read the minute endothermic peak.

In addition, the method of reading the minute endothermic peak is implemented according to the following description. First, draw a straight line parallel to the Y axis and a baseline at the values of 135°C and 155°C in the differential scanning calorimetry chart, and find the curve from the graph and the two straight lines parallel to the Y axis and the baseline. The area of the heat-absorbing side enclosed. Similarly, for 140°C and 160°C, 145°C and 165°C, 150°C and 170°C, 155°C and 175°C, 160°C and 180°C, 165°C and 185°C, 170°C and 190°C, 175°C and 195°C ℃, 180℃ and 200℃, 185℃ and 205℃, 190℃ and 210℃, 195℃ and 215℃, 200℃ and 220℃, 205℃ and 225℃, 210℃ and 230℃, 215℃ and 235℃, Areas are also calculated at 17 locations at 220°C and 240°C. The heat absorption of a small peak is usually 0.2 J/g or more and 5.0 J/g or less. Therefore, only data with an area of 0.2 J/g or more and 5.0 J/g or less are treated as valid data. Among the 18 area data in total, the peak temperature of the endothermic peak in the temperature region of the data showing the largest area as the effective data is set as the minute peak temperature. When there is no valid data, it is set as no small peak temperature.

Furthermore, the minute peak temperature can be adjusted by the processing temperature (heat-fixing temperature) in the heat-fixing step described later.

(Polyester) The biaxially stretched polyester film contains polyester. The type of polyester is not particularly limited, and as the polyester, a known one can be selected.

Examples of polyesters include linear saturated polyesters synthesized from aromatic dibasic acids or ester-forming derivatives of aromatic dibasic acids and diols or ester-forming derivatives of diols. Specific examples of linear saturated polyesters include polyethylene terephthalate, polyethylene isophthalate, polybutylene terephthalate, and poly(1,4-terephthalate). Cyclohexyl dimethyl ester), polyethylene-2,6-naphthalate, etc. Among them, as polyester, from the viewpoint of the balance of mechanical properties and cost, polyethylene terephthalate, polyethylene-2,6-naphthalate, and poly(terephthalic acid) are particularly preferred. 1,4-cyclohexyl dimethyl ester).

The polyester may be a homopolymer or a copolymer. Furthermore, the polyester may contain a small amount of other types of resin (for example, polyimide, etc.).

The type of polyester is not limited to the above-mentioned polyester, and a known polyester may also be used. As a known polyester, a dicarboxylic acid component and a diol component can be used for synthesis, or a commercially available polyester can also be used.

When synthesizing polyester, for example, a method of subjecting (a) a dicarboxylic acid component and (b) a diol component to at least one reaction of an esterification reaction and a transesterification reaction by a well-known method is mentioned.

(A) The dicarboxylic acid component includes, for example, malonic acid, succinic acid, glutaric acid, adipic acid, suberic acid, sebacic acid, dodecanedioic acid, dimer acid, eicosane Aliphatic dicarboxylic acids such as diacid, pimelic acid, azelaic acid, methylmalonic acid, ethylmalonic acid, etc.; adamantane dicarboxylic acid, norbornene dicarboxylic acid, cyclohexane dicarboxylic acid, ten Alicyclic dicarboxylic acids such as hydronaphthalene dicarboxylic acid; terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid Formic acid, 1,8-naphthalenedicarboxylic acid, 4,4'-diphenyl dicarboxylic acid, 4,4'-diphenyl ether dicarboxylic acid, isophthalic acid-5-sodium sulfonate, phenyl indan Dicarboxylic acids such as aromatic dicarboxylic acids such as dicarboxylic acid, anthracene dicarboxylic acid, phenanthrene dicarboxylic acid, 9,9'-bis(4-carboxyphenyl) benzoic acid, or ester derivatives of dicarboxylic acids.

(B) The glycol component includes, for example, ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,2-butanediol, and 1,3-butanediol Aliphatic diols such as alcohols; alicyclic diols such as cyclohexanedimethanol, spirodiol, isosorbide; bisphenol A, 1,3-benzenedimethanol, 1,4-benzenedimethanol, Diol compounds such as aromatic diols such as 9,9'-bis(4-hydroxyphenyl)pyridium.

As the (a) dicarboxylic acid component, it is preferable to use at least one kind of aromatic dicarboxylic acid. It is more preferable to contain an aromatic dicarboxylic acid among the dicarboxylic acid components as a main component. In addition, the "main component" means that the ratio of the aromatic dicarboxylic acid to the dicarboxylic acid component is 80% by mass or more. (A) As a dicarboxylic acid component, you may contain dicarboxylic acid components other than aromatic dicarboxylic acid. Such dicarboxylic acid components are ester derivatives such as aromatic dicarboxylic acids and the like.

As the (b) diol component, it is preferable to use at least one kind of aliphatic diol. As the aliphatic diol, ethylene glycol may be contained, and ethylene glycol is preferably contained as a main component. In addition, the term "main component" means that the proportion of ethylene glycol in the glycol component is 80% by mass or more.

The amount of aliphatic diol (for example, ethylene glycol, etc.) used is preferably 1 mol of aromatic dicarboxylic acid (for example, terephthalic acid, etc.) and optionally an ester derivative of aromatic dicarboxylic acid The range of 1.015 mol to 1.50 mol. The use amount of the aliphatic diol is more preferably in the range of 1.02 mol to 1.30 mol, and still more preferably in the range of 1.025 mol to 1.10 mol. If the use amount of the aliphatic diol is in the range of 1.015 mol or more, the esterification reaction is likely to proceed. In addition, if the amount of the aliphatic diol used is in the range of 1.50 mol or less, for example, the by-production of diethylene glycol caused by the dimerization of ethylene glycol can be suppressed, so that the melting point of the polyester can be maintained well. And glass transition temperature, crystallinity, heat resistance, hydrolysis resistance, and weather resistance.

In the esterification reaction or the transesterification reaction, a known reaction catalyst can be used. Examples of the reaction catalyst include alkali metal compounds, alkaline earth metal compounds, zinc compounds, lead compounds, manganese compounds, cobalt compounds, aluminum compounds, antimony compounds, titanium compounds, and phosphorus compounds. The reaction catalyst is usually added at any stage before the esterification reaction or the transesterification reaction of the polyester is completed. As the reaction catalyst, antimony compounds, germanium compounds, and titanium compounds are preferred. For example, when a germanium compound is used as the reaction catalyst, it is preferable to directly use the powder of the germanium compound.

The esterification reaction is performed, for example, by polymerizing an aromatic dicarboxylic acid and an aliphatic diol in the presence of a reaction catalyst containing a titanium compound. In the esterification reaction, it is preferable to use an organotitanium chelate complex with an organic acid as a ligand as the titanium compound as a reaction catalyst, and to add the organotitanium chelate complex at least sequentially during the reaction. The process of phosphates, magnesium compounds, and pentavalent phosphates that do not have aromatic rings as substituents.

Specifically, in the esterification reaction, first, an aromatic dicarboxylic acid and an aliphatic diol are mixed with a reaction catalyst containing an organic titanium chelate complex as a titanium compound. Titanium compounds such as organotitanium chelate complexes also show high catalytic activity for esterification reactions, and therefore can promote the progress of esterification reactions. In this case, the titanium compound can be added after mixing the aromatic dicarboxylic acid component and the aliphatic diol component, or the aliphatic diol can be added after mixing the aromatic dicarboxylic acid component (or aliphatic diol component) and the titanium compound Ingredients (or aromatic dicarboxylic acid ingredients). In addition, an aromatic dicarboxylic acid component, an aliphatic diol component, and a titanium compound may be mixed at the same time. The mixing method is not particularly limited, and a known method can be selected.

When synthesizing the polyester, it is also preferable to add the following pentavalent phosphorus compound as an additive. As the pentavalent phosphorus compound, at least one kind of pentavalent phosphoric acid ester which does not have an aromatic ring as a substituent is mentioned. The pentavalent phosphorus compound is preferably a phosphate ester [(OR) ₃ -P=O; R is an alkyl group with 1 or 2 carbons] having a lower alkyl group having 2 or less carbons as a substituent, more preferably Trimethyl phosphate, triethyl phosphate.

As the addition amount of the phosphorus compound, it is preferable that the phosphorus (P) element conversion value becomes an amount in the range of 50 ppm to 90 ppm with respect to the polyester after synthesis. The amount of the phosphorus compound is more preferably an amount where the phosphorus (P) element conversion value becomes 60 ppm to 80 ppm, and even more preferably an amount where the phosphorus (P) element conversion value becomes 60 ppm to 75 ppm.

In addition, when synthesizing polyester, it is also preferable to add a magnesium compound as an additive. By containing a magnesium compound in the polyester, the electrostatic applicability of the polyester is improved. Examples of magnesium compounds include magnesium salts such as magnesium oxide, magnesium hydroxide, magnesium alkoxide, magnesium acetate, and magnesium carbonate. Among them, from the viewpoint of solubility to ethylene glycol, magnesium acetate is preferred.

As the addition amount of the magnesium compound, in order to impart high electrostatic applicability, it is preferable that the magnesium (Mg) element conversion value becomes 50 ppm or more relative to the synthesized polyester, and it is more preferable that the magnesium (Mg) element conversion value becomes Amount in the range of 50 ppm to 100 ppm. From the viewpoint of imparting electrostatic applicability, the addition amount of the magnesium compound is preferably an amount in the range of 60 ppm to 90 ppm, and more preferably an amount in the range of 70 ppm to 80 ppm.

In the esterification reaction, it is preferable to add a titanium compound as a reaction catalyst and a magnesium compound and phosphorus as additives so that the value Z calculated according to the following formula (i) satisfies the following relational formula (ii) Compound to synthesize polyester (preferably melt polymerization). Here, the phosphorus (P) content is the amount of phosphorus derived from the entire phosphorus compound containing a pentavalent phosphate ester without an aromatic ring, and the titanium (Ti) content is derived from the entire titanium compound containing the organic titanium chelate complex. The amount of titanium. In this way, in the esterification reaction, a magnesium compound and a phosphorus compound are used together in a system containing a titanium compound, and the timing and ratio of addition of the magnesium compound and the phosphorus compound are controlled, thereby appropriately reducing the catalyst of the titanium compound. The activity is maintained high, and a polyester with a less yellow hue is obtained. That is, the esterification reaction is carried out by the above method, and even if it is exposed to high temperature during the esterification reaction or during film formation (for example, during melting), etc., it is difficult to produce yellow coloring and is imparted with heat resistance. Of polyester. (I) Z=5×(P content[ppm]/P atomic weight)-2×(Mg content[ppm]/Mg atomic weight)-4×(Ti content[ppm]/Ti atomic weight) (Ii) 0≦Z≦5.0

The phosphorus compound not only acts on the titanium compound, but also acts on the magnesium compound. Therefore, the above-mentioned formula (i) is an indicator that quantitatively expresses the balance of the three. The formula (i) represents the amount of phosphorus that can act on the titanium compound by removing the amount of phosphorus that can act on the magnesium compound from the total amount of phosphorus that can be reacted. It can be said that when the value Z is positive, the phosphorus atoms acting on the titanium compound are in a remaining state, on the contrary, when the value Z is negative, the phosphorus atoms required to act on the titanium compound are in a state of insufficient . In the reaction, each atom of Ti, Mg, and P is not equivalent. Therefore, the molar number of each of the formula (i) is multiplied by the valence and weighted.

Furthermore, for the synthesis of the polyester, inexpensive and easily available titanium compounds, the above-mentioned phosphorus compounds, and magnesium compounds can be used. While having the reactivity required for the reaction, a polyester having excellent heat resistance can be obtained.

In formula (ii), from the viewpoint of further improving the heat resistance of the polyester while maintaining the polymerization reactivity, it is preferable to satisfy 1.0≦Z≦4.0, and more preferably to satisfy 1.5≦Z≦3.0 condition.

As a suitable form of the esterification reaction, it is preferable to add 1 ppm to 30 ppm of citric acid or citrate as a ligand to the aromatic dicarboxylic acid and aliphatic diol before the esterification reaction is completed. Titanium chelate complexes. Thereafter, it is preferable to add a magnesium salt of a weak acid of 60 ppm to 90 ppm (more preferably 70 ppm to 80 ppm) in the presence of a titanium chelate complex, and then add 60 ppm to 80 ppm ( More preferably, it is a pentavalent phosphate ester that does not have an aromatic ring as a substituent of 65 ppm to 75 ppm).

The esterification reaction can be carried out using a multi-stage device connecting at least two reaction tanks in series, under the condition of ethylene glycol reflux, while removing water or alcohol generated by the reaction to the outside of the system.

The esterification reaction can be carried out in one stage or divided into multiple stages. When the esterification reaction is performed in one stage, the esterification reaction temperature is preferably 230°C to 260°C, more preferably 240°C to 250°C. When the esterification reaction is carried out in multiple stages, the temperature of the esterification reaction in the first reaction tank is preferably 230°C to 260°C, more preferably 240°C to 250°C, and the pressure in the reaction tank is preferably 1.0 kg/ cm ² ～5.0 kg/cm ² , more preferably 2.0 kg/cm ² ～3.0 kg/cm ² . The temperature of the esterification reaction in the second reaction tank is preferably 230°C to 260°C, more preferably 245°C to 255°C, and the pressure in the reaction tank is 0.5 kg/cm ² to 5.0 kg/cm ² , more preferably 1.0 kg/cm ² ～3.0 kg/cm ² . Furthermore, when performing the esterification reaction in three or more stages, it is preferable to set the conditions of the esterification reaction in the intermediate stage to the conditions between the first reaction tank and the final reaction tank.

On the other hand, the esterification reaction product produced by the esterification reaction is subjected to a polycondensation reaction to produce a polycondensate. The polycondensation reaction can be carried out in one stage or divided into multiple stages.

The esterification reaction products such as oligomers generated by the esterification reaction are continuously supplied to the polycondensation reaction. The polycondensation reaction can be suitably carried out by supplying the esterification reaction product to a multi-stage polycondensation reaction tank.

For example, as the conditions of the polycondensation reaction when the polycondensation reaction is carried out in a three-stage reaction tank, the conditions shown below are preferable. The first reaction tank is preferably in the following form: the reaction temperature is 255°C to 280°C, more preferably 265°C to 275°C, and the pressure in the first reaction tank is 100 torr-10 torr (13.3×10 ^-3 MPa～ 1.3×10 ^-3 MPa), more preferably 50 torr～20 torr (6.67×10 ^-3 MPa～2.67×10 ^-3 MPa). The second reaction tank is preferably in the following form: the reaction temperature is 265°C to 285°C, more preferably 270°C to 280°C, and the pressure in the second reaction tank is 20 torr～1 torr (2.67×10 ^-3 MPa～ 1.33×10 ^-4 MPa), more preferably 10 torr～3 torr (1.33×10 ^-3 MPa～4.0×10 ^-4 MPa). The third reaction tank as the final reaction tank is preferably in the following form: the reaction temperature is 270°C to 290°C, more preferably 275°C to 285°C, and the pressure is 10 torr to 0.1 torr (1.33×10 ^-3 MPa to 1.33 ×10 ^-5 MPa), more preferably 5 torr～0.5 torr (6.67×10 ^-4 MPa～6.67×10 ^-5 MPa).

The polyester synthesized in the above method may further contain additives such as light stabilizers, antioxidants, ultraviolet absorbers, flame retardants, lubricants (fine particles), nucleating agents (crystallization agents), crystallization inhibitors, etc. .

The polyester is preferably polymerized by an esterification reaction and then subjected to solid-phase polymerization. By solid-phase polymerization of polyester, the water content, crystallinity, acid value of the polyester, that is, the concentration (AV) of the terminal carboxyl group (COOH group) of the polyester (AV), and the inherent viscosity can be controlled. In particular, it is preferable to increase the concentration of Ethylene Glycol (EG) gas at the beginning of the solid-phase polymerization within the range of 200 ppm to 1000 ppm compared to the EG gas concentration at the end of the solid-phase polymerization, and it is more preferable to From 250 ppm to 800 ppm, and more preferably from 300 ppm to 700 ppm, increase the concentration of ethylene glycol (EG) gas at the start of solid-phase polymerization to perform solid-phase polymerization. At this time, the AV can be controlled by increasing the average EG gas concentration (the average of the gas concentration at the beginning and the end of the solid-phase polymerization). That is, by adding EG to make the terminal hydroxyl group of EG react with the terminal COOH group, AV can be reduced. The difference between the EG gas concentration at the beginning of the solid-phase polymerization and the EG gas concentration at the end of the solid-phase polymerization is preferably 100 ppm to 500 ppm, more preferably 150 ppm to 450 ppm, and even more preferably 200 ppm to 400 ppm.

In addition, the temperature of the solid phase polymerization is preferably 180°C to 230°C, more preferably 190°C to 215°C, and still more preferably 195°C to 209°C. In addition, the solid phase polymerization time is preferably 10 hours to 40 hours, more preferably 14 hours to 35 hours, and still more preferably 18 hours to 30 hours.

Here, the polyester preferably has high hydrolysis resistance. Therefore, the concentration of terminal carboxyl groups in the polyester is preferably 50 equivalents/t (here, t means ton. Furthermore, ton means 1000 kg) or less, more preferably 35 equivalents/t or less, and further More preferably, it is 20 equivalents/t or less. If the concentration of the terminal carboxyl group is 50 equivalent/t or less, the hydrolysis resistance can be maintained, and the decrease in strength over time with heat and humidity can be reduced. From the viewpoint of maintaining the adhesion between the substrate and the adjacent layer, the lower limit of the concentration of the terminal carboxyl group is preferably 2 equivalents/t, and more preferably 3 equivalents/t. The concentration of terminal carboxyl groups in the polyester can be adjusted by the type of reaction catalyst, film forming conditions (film forming temperature and time), solid-phase polymerization, and additives (end-capping agent, etc.).

-Carbodiimide compounds, enoneimine compounds- The polyester may contain at least one of a carbodiimide compound and a keteneimine compound. The carbodiimide compound and the enoneimine compound may be used alone, respectively, or both may be used in combination. This suppresses the deterioration of polyester in a hot and humid environment, and is effective for maintaining high insulation even in a hot and humid environment.

The carbodiimide compound or ketimine compound is preferably contained in an amount of 0.1% to 10% by mass relative to the total mass of the polyester, and more preferably, it is contained in an amount of 0.1% to 4% by mass. The compound or the ketene imine compound more preferably contains 0.1% by mass to 2% by mass of the carbodiimide compound or ketene imine compound. By setting the content of the carbodiimide compound or the enoneimine compound within the above range, the adhesion between the substrate and the adjacent layer can be further improved. In addition, the heat resistance of the substrate can be improved. Furthermore, when the carbodiimide compound and the enoneimine compound are used in combination, it is preferable that the sum of the contents of the two compounds is within the above-mentioned range.

Examples of the carbodiimide compound include compounds having one or more carbodiimide groups in the molecule (including polycarbodiimide compounds). Specifically, as the monocarbodiimide compound, for example, dicyclohexylcarbodiimide, diisopropylcarbodiimide, dimethylcarbodiimide, and diisobutyl carbon can be exemplified. Diethylimid, dioctylcarbodiimide, tertiary butyl isopropyl carbodiimide, diphenylcarbodiimide, di-tertiary butylcarbodiimide, di- β-naphthylcarbodiimide, N,N'-di-2,6-diisopropylphenylcarbodiimide, etc. As the polycarbodiimide compound, for example, the lower limit of the degree of polymerization is usually 2 or more, preferably 4 or more, and the upper limit of the degree of polymerization is usually 40 or less, preferably 30 or less. Specifically, as the polycarbodiimide compound, there can be cited the specification of U.S. Patent No. 2941956, Japanese Patent Publication No. 47-33279, "Journal of Organic Chemistry (J.Org.Chem.)" 28, pp. 2069-2075 (1963), and "Chemical Review" 1981, Volume 81, No. 4, pp.619-621, etc.

Examples of the organic diisocyanate as a raw material for the production of the polycarbodiimide compound include aromatic diisocyanates, aliphatic diisocyanates, alicyclic diisocyanates, and mixtures of these. Specifically, examples of organic diisocyanates include 1,5-naphthalene diisocyanate, 4,4'-diphenylmethane diisocyanate, 4,4'-diphenyldimethylmethane diisocyanate, 1,3 -Phenylene diisocyanate, 1,4-phenylene diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, a mixture of 2,4-toluene diisocyanate and 2,6-toluene diisocyanate , Hexamethylene diisocyanate, cyclohexane-1,4-diisocyanate, xylylene diisocyanate (xylylene diisocyanate), isophorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, methyl Cyclohexane diisocyanate, tetramethylxylylene diisocyanate, 2,6-diisopropylphenyl isocyanate, 1,3,5-triisopropylbenzene-2,4-diisocyanate, etc.

Examples of specific polycarbodiimide compounds that can be obtained industrially include: Carbodilite (registered trademark) HMV-8CA (manufactured by Nisshinbo Chemical Co., Ltd.) and Carbodilite (Registered trademark) LA-1 (manufactured by Nisshinbo Chemical Co., Ltd.), Stabaxol (registered trademark) P (manufactured by Rhein Chemie), Stabaxol (registered trademark) P100 (manufactured by Rhein Chemie), Stabaxol (registered trademark) P400 (manufactured by Rhein Chemie), Stabilizer 9000 (manufactured by Raschig), etc.

The carbodiimide compound may be used alone, or a plurality of compounds may be mixed and used.

As the enoneimine compound, it is preferable to use the enoneimine compound represented by the following general formula (K-A).

[化1]

In the general formula (KA), R ¹ and R ² each independently represent an alkyl group, an aryl group, an alkoxy group, an alkoxycarbonyl group, an aminocarbonyl group, an aryloxy group, an acyl group or an aryloxycarbonyl group, and R ³ represents Alkyl or aryl.

Here, it is preferable that the molecular weight of the part other than the ^{nitrogen atom and the substituent R 3} bonded to the nitrogen atom of the ketene imine compound is 320 or more. That is, in the general formula (KA), ^{the molecular weight of the R 1} -C(=C)-R ² group is preferably 320 or more. The molecular weight of the part of the ketenimine compound other than the nitrogen atom and the substituent R ³ bonded to the nitrogen atom is more preferably 500 to 1,500, and still more preferably 600 to 1,000. In this way, by setting ^{the molecular weight of the part other than the nitrogen atom and the substituent R 3} bonded to the nitrogen atom within the above range, the adhesion between the substrate and the adjacent layer can be improved. The reason is that since the part other than the nitrogen atom and the substituent R ³ bonded to the nitrogen atom has a molecular weight within a fixed range, the bulky polyester terminal to a certain extent diffuses into the layer adjacent to the substrate And play an anchoring effect.

The molar molecular weight of the enoneimine compound (mole molecular weight/the number of the enoneimine portion) relative to the number of the enoneimine part (>C=C=N-) in the enoneimine compound is preferable It is 1000 or less, more preferably 500 or less, and still more preferably 400 or less. By setting the molecular weight of the substituent on the carbon of the keteneimine part of the keteneimine compound and the molar molecular weight of the keteneimine compound relative to the number of the keteneimine part within the above range, it is possible to suppress The volatilization of the ketene imine compound itself, and suppresses the volatilization of the ketene compound generated when the terminal carboxyl group of the polyester is blocked, and the ketene imine compound can be used to seal the terminal carboxyl group of the polyester with a low addition amount. end.

For the enoneimine compound having at least one enoneimine moiety, for example, refer to the method described in "J. Am. Chem. Soc.", 1953, 75(3), pp657-660, etc. To synthesize.

[Undercoating] The laminated polyester film includes an undercoat layer by applying the undercoat layer forming composition to one surface of the polyester film stretched in the first direction before extending in the second direction, and It is formed by stretching in the second direction, and the modulus of elasticity is 0.7 GPa or more.

(Modulus of Elasticity) If the elastic modulus of the primer layer is 0.7 GPa or more, the laminated polyester film has excellent resistance to aggregation destruction. The elastic modulus of the primer layer is preferably 1.0 GPa or more, more preferably 1.3 GPa or more. The elastic modulus of the primer layer is preferably 2.0 GPa or less, more preferably 1.7 GPa or less. If the modulus of elasticity of the primer layer is in the above range, the resistance to aggregation destruction when a laminated film is formed is further improved. The elastic modulus of the undercoat layer can be adjusted by the type of resin component contained in the undercoat layer. When a crosslinking agent is included, it can also be adjusted by the type or amount of the crosslinking agent.

The elastic modulus of the primer layer can be measured by the following method. The composition for forming an undercoat layer was applied to a polyethylene terephthalate (PET) film treated with a release agent so that the film thickness after drying became 15 μm. ), Cerapeel (registered trademark)), and dried at 170°C for 2 minutes, thereby forming a primer layer on the PET film. The primer layer was cut into a size of 3 cm×5 mm, and the primer layer was peeled from the PET film. For the obtained primer, the primer was tested at a speed of 50 mm/min using a tensile testing machine (Tensilon: manufactured by A&D) at a temperature of 23.0°C and a relative humidity of 50.0%. Tensile test, and determine the modulus of elasticity.

(In-line coating method) The primer layer is formed by applying the primer layer forming composition to one surface of the polyester film stretched in the first direction, and coating the primer layer forming composition The polyester film of is extended along the surface of the film in a second direction orthogonal to the first direction. That is, the undercoat layer is formed by a so-called in-line coating method, which is different from the off-line coating method in which the film is wound up in the middle of the production of the laminated polyester film and then applied separately. By forming the primer layer by the in-line coating method, the adhesion between the layers of the laminated polyester film becomes good, and it is also advantageous from the viewpoint of productivity.

The thickness of the undercoat layer is preferably 0.01 μm to 1 μm. The thickness of the undercoat layer is preferably 0.01 μm or more, more preferably 0.03 μm or more, and still more preferably 0.05 μm or more. In addition, the thickness of the primer layer is preferably 1 μm or less, more preferably 0.8 μm or less, and still more preferably 0.7 μm or less.

(Composition for forming primer layer) The primer layer is formed by using a solution prepared by dissolving the following resin components in a suitable solvent or a dispersion prepared by dispersing the resin component in a dispersion medium as the composition for forming the primer layer. It is applied to a polyester film stretched in the first direction and stretched in a second direction orthogonal to the first direction along the film surface. In addition to the resin component and the solvent or dispersion medium, the composition for forming an undercoat layer may contain other additives as necessary. In view of environmental considerations, it is preferable to use an aqueous dispersion dispersed in water as the composition for forming an undercoat layer.

In one embodiment of the present invention, the method for obtaining the aqueous dispersion is not particularly limited. As a method for obtaining an aqueous dispersion, for example, as exemplified in Japanese Patent Laid-Open No. 2003-119328, etc., it is preferable to treat the resin component, water, and optionally an organic solvent in a sealable container. The method of heating and stirring. According to this method, even if a non-volatile water-based auxiliary agent is not added substantially, the resin component can be made into an aqueous dispersion satisfactorily, so it is suitable as a method for obtaining an aqueous dispersion.

The solid content of the resin component in the aqueous dispersion is not particularly limited, but from the viewpoints of ease of application and ease of adjustment of the thickness of the primer layer, it is preferably 1 relative to the total mass of the aqueous dispersion. Mass%-60% by mass, more preferably 2% by mass to 50% by mass, and still more preferably 5% by mass to 30% by mass.

-Resin composition- The resin component contained in the primer layer can be formed into a layer by an in-line coating method, and it is not particularly limited as long as the modulus of elasticity at the time of forming the primer layer can be 0.7 GPa or more. Examples of the resin component contained in the primer layer include acrylic resins, polyester resins, polyolefin resins, and silicone compounds. It is more preferable that the undercoat layer contains an acrylic resin, and the content ratio of the acrylic resin in the resin component contained in the undercoat layer is 50% by mass or more, and more preferably 75% by mass or more. If 50% by mass or more of the resin component is acrylic resin, it is easy to adjust the elastic modulus of the undercoat layer to 0.7 GPa or more, and the aggregation destruction resistance when the laminated film is formed is further improved.

～Acrylic resin～ As the acrylic resin, for example, a polymer containing polymethyl methacrylate, polyethyl acrylate, polybutyl methacrylate, and the like is preferable. As the acrylic resin, commercially available products on the market can be used, for example, AS-563A (manufactured by Daicel FineChem (Stock)), Julimer (registered trademark) ET-410, Julimer SEK-301 (all manufactured by Japan Pure Chemical Industries (Stock)). From the viewpoint of the modulus of elasticity at the time of forming the primer layer, the acrylic resin is more preferably an acrylic resin containing polymethyl methacrylate and polyethyl acrylate, and still more preferably an acrylic resin containing a styrene skeleton Resin.

～Polyester resin～ As the polyester resin, for example, polyethylene terephthalate (PET), polyethylene-2,6-naphthalate (PEN), and the like are preferable. As the polyester resin, commercially available products that are already on the market can be used. For example, Vylonal (registered trademark) MD-1245 (manufactured by Toyobo Co., Ltd.) can be preferably used.

～Polyurethane resin～ As the polyurethane resin, for example, a carbonate-based urethane resin is preferable. For example, Superflex (registered trademark) 460 (Daiichi Kogyo Pharmaceutical Co., Ltd.) is preferably used. manufacture).

～Polyolefin resin～ As the polyolefin resin, for example, a modified polyolefin copolymer is preferable. As the polyolefin resin, commercially available products on the market can be used, for example: Alowbase (registered trademark) SE-1013N, SD-1010, TC-4010, TD-4010 (all Unijik (Manufactured by Unitika (Stock)), Hytec S3148, S3121, S8512 (all manufactured by Toho Chemical (Stock)), Chemipearl (registered trademark) S-120, S-75N, V100 , EV210H (all manufactured by Mitsui Chemicals (Stock)), etc. Among them, from the viewpoint of improving the adhesion, it is preferable to use Alowbase (registered trademark) SE-1013N ( Unigeco (manufactured by shares)). In addition, the acid-modified polyolefin described in paragraph [0022] to paragraph [0034] of JP 2014-76632 A can also be preferably used.

～Silicone compounds～ As a silicone compound, the compound which has a (poly)siloxane structural unit mentioned later is preferable. As the silicone compound, commercially available products on the market can be used, for example, Ceranate (registered trademark) WSA1060, Ceranate WSA1070 (all manufactured by DIC) ), and H7620, H7630, H7650 (all manufactured by Asahi Kasei Chemicals (Stock)).

-Other additives- As other additives, corresponding to the function imparted to the undercoat layer, for example, a crosslinking agent for enhancing the strength of the film, a surfactant, an antioxidant, and an antiseptic for enhancing the uniformity of the coating film, etc. can be cited.

～Crosslinking agent～ The composition for forming an undercoat layer preferably contains a crosslinking agent. When the composition for forming an undercoat layer contains a crosslinking agent, a crosslinked structure is formed in the resin component contained in the composition for forming an undercoat layer, and a layer with further improved adhesion and film strength is formed. That is, the undercoat layer formed using the composition for forming an undercoat layer containing a crosslinking agent contains a crosslinking agent, and has excellent adhesiveness and film strength with an adjacent layer.

Examples of the crosslinking agent include crosslinking agents such as epoxy-based crosslinking agents, isocyanate-based crosslinking agents, melamine-based crosslinking agents, carbodiimide-based crosslinking agents, and oxazoline-based crosslinking agents. Among them, the oxazoline-based crosslinking agent is particularly preferred from the viewpoint of ensuring the adhesiveness between the primer layer and the base material after the damp heat over time. That is, the primer layer preferably contains an oxazoline-based crosslinking agent.

Specific examples of the oxazoline-based crosslinking agent include: 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl 2-oxazoline, 2-isopropenyl-2-oxazoline, 2-isopropenyl-4-methyl-2-oxazoline, 2-isopropenyl-5-ethyl-2- Oxazoline, 2,2'-bis-(2-oxazoline), 2,2'-methylene-bis-(2-oxazoline), 2,2'-ethylene-bis-( 2-oxazoline), 2,2'-trimethylene-bis-(2-oxazoline), 2,2'-tetramethylene-bis-(2-oxazoline), 2, 2' -Hexamethylene-bis-(2-oxazoline), 2,2'-octamethylene-bis-(2-oxazoline), 2,2'-ethylene-bis-(4, 4'-Dimethyl-2-oxazoline), 2,2'-p-phenylene-bis-(2-oxazoline), 2,2'-m-phenylene-bis-(2-oxazoline) Oxazoline), 2,2'-methylene phenyl-bis-(4,4'-dimethyl-2-oxazoline), bis-(2-oxazoline cyclohexane) sulfide, double -(2-oxazoline-norbornane) sulfide and the like. Furthermore, (co)polymers of these compounds can also be preferably used.

In addition, oxazoline-based crosslinking agents can be used commercially available products, for example: Epocros (registered trademarks) K2010E, K2020E, K2030E, WS500, WS700 (all of which are from Japan Shokubai Chemical Industry Co., Ltd.) (Stock) Manufacturing) and so on.

Only one type of crosslinking agent may be used, or two or more types may be used in combination. The addition amount of the crosslinking agent is preferably in the range of 1 part by mass or more and 30 parts by mass or less with respect to 100 parts by mass of the resin component, and more preferably in the range of 5 parts by mass or more and 25 parts by mass or less.

～Catalyst of crosslinking agent～ In the composition for forming an undercoat layer, a crosslinking agent and a catalyst of a crosslinking agent may be used in combination. When the undercoat layer forming composition contains the catalyst of the crosslinking agent, the crosslinking reaction between the resin component and the crosslinking agent is promoted, and the solvent resistance of the undercoat layer can be improved. In addition, the crosslinking reaction progresses well, and the film strength and dimensional stability of the primer layer are further improved. In particular, when a crosslinking agent having an oxazoline group (oxazoline-based crosslinking agent) is used as the crosslinking agent, it is preferable to use a catalyst of the crosslinking agent.

As a catalyst of a crosslinking agent, an onium compound is mentioned, for example. As the onium compound, an ammonium salt, a sulfonium salt, an oxonium salt, an iodonium salt, a phosphonium salt, a nitronium salt, a nitrosium salt, a diazonium salt, etc. can be suitably mentioned.

Specific examples of onium compounds include: monoammonium phosphate, diammonium phosphate, ammonium chloride, ammonium sulfate, ammonium nitrate, ammonium p-toluenesulfonate, ammonium sulfamate, ammonium imidinodisulfonate, tetrabutyl chloride Base ammonium, benzyl trimethyl ammonium chloride, triethyl benzyl ammonium chloride, tetrabutyl ammonium boron tetrafluoride, tetrabutyl ammonium phosphate hexafluoride, tetrabutyl ammonium perchlorate, tetrabutyl sulphate Ammonium salts such as base ammonium; Trimethyl alumium iodide, boron tetrafluoride trimethyl alumium, boron tetrafluoride diphenylmethyl alumium, boron tetrafluoride benzyl tetramethylene alumium, antimony hexafluoride 2-butenyl tetramethylene Methyl sulfonium, antimony hexafluoride 3-methyl-2-butenyl tetramethylene sulfonium, etc.; Oxonium salts such as boron tetrafluoride and trimethyloxonium; Diphenyl iodonium chloride, boron tetrafluoride diphenyl iodonium and other iodonium salts; Antimony hexafluoride cyanomethyltributylphosphonium, boron tetrafluoride ethoxycarbonylmethyltributylphosphonium and other phosphonium salts; Nitroium salts such as boron tetrafluoride nitronium; Nitrosium salts such as boron tetrafluoride and nitrosium; Diazonium salts such as 4-methoxybenzenediazonium chloride, etc.

Among them, from the viewpoint of shortening the curing time, the onium compound is more preferably an ammonium salt, a sulfonium salt, an iodonium salt, or a phosphonium salt, and even more preferably an ammonium salt. In addition, from the viewpoints of safety, pH, and cost, phosphate-based onium compounds and benzyl chloride-based onium compounds are preferred. The onium compound is particularly preferably diammonium phosphate.

As the catalyst of the crosslinking agent, only one type may be used, or two or more types may be used in combination. With respect to the crosslinking agent in the undercoat layer forming composition, the addition amount of the catalyst of the crosslinking agent is preferably in the range of 0.1% by mass to 15% by mass, and more preferably 0.5% by mass to 12% by mass The following range is more preferably a range of 1% by mass or more and 10% by mass or less, and particularly preferably 2% by mass or more and 7% by mass or less. The addition amount of the catalyst of the crosslinking agent with respect to the crosslinking agent is 0.1% by mass or more, which means that the catalyst containing the crosslinking agent is actively contained. In the composition for forming an undercoat layer, the catalyst containing the cross-linking agent facilitates the cross-linking reaction between the resin component and the cross-linking agent, and further excellent solvent resistance can be obtained. In addition, from the viewpoint of solubility, filterability of the coating liquid, and adhesion to adjacent layers, it is advantageous that the content of the catalyst of the crosslinking agent is 15% by mass or less.

In order to improve the productivity of the undercoat layer by the in-line coating method, that is, the film forming speed, the aqueous dispersion may contain a non-volatile water-based auxiliary agent such as a surfactant or an emulsifier. By selecting the appropriate non-volatile water-based additives, productivity and various properties can be coexisted more effectively. Here, the non-volatile water-based auxiliary agent refers to a non-volatile compound that contributes to the dispersion or stabilization of the resin component. Examples of non-volatile water-based auxiliary agents include cationic surfactants, anionic surfactants, nonionic surfactants, amphoteric surfactants, fluorine-based surfactants, and reactive surfactants. Agent, water-soluble polymer, etc. As the non-volatile water-based auxiliary agent, in addition to those usually used for emulsion polymerization, it also contains emulsifiers, and particularly preferably fluorine-based surfactants and nonionic surfactants. Since the fluorine-based surfactant and the nonionic surfactant are nonionic, they do not become a catalyst for the decomposition of polyester, and therefore have excellent weather resistance. Relative to the aqueous coating liquid, the addition amount of the surfactant is preferably 1 ppm to 100 ppm, more preferably 5 ppm to 70 ppm, and particularly preferably 10 ppm to 50 ppm.

[Manufacturing method of laminated polyester film] The manufacturing method of the laminated polyester film includes the step of stretching the unstretched polyester film in the first direction; Step on one side; stretch the polyester film coated with the composition for forming an undercoat layer in a second direction orthogonal to the first direction to form an undercoat layer having an elastic modulus of 0.7 GPa or more Step; and a heat-fixing step of heat-fixing the polyester film formed with the primer layer at 165° C. or higher and 215° C. or lower.

(Extend in the first direction) The manufacturing method of the laminated polyester film includes the step of extending the unstretched polyester film in the first direction.

The unstretched polyester film, for example, uses the polyester as the raw material resin, the raw material resin is dried and then melted, and the obtained melt is passed through a gear pump or a filter, and then is extruded through a die until it is cooled. Roll it on and allow it to cool and solidify, thereby obtaining it as an unstretched polyester film. Melting is preferably performed using an extruder, and as the extruder, a single-screw extruder may be used, or a twin-screw extruder may also be used.

The extrusion is preferably performed under vacuum exhaust or inert gas environment. The temperature of the extruder is preferably the melting point of the polyester used-the melting point + 80°C or less, more preferably the melting point + 10°C or more, the melting point + 70°C or less, and still more preferably the melting point + 20°C or more, the melting point +60°C or less range. If the temperature of the extruder is the melting point + 10°C or higher, the polyester is sufficiently melted. On the other hand, if the temperature is the melting point + 70°C or lower, the decomposition of the polyester is suppressed, which is preferable. Furthermore, the polyester is preferably dried before being put into the extruder, and the moisture content of the dried polyester is preferably 10 ppm to 300 ppm, more preferably 20 ppm to 150 ppm.

In order to improve the hydrolysis resistance of the unstretched polyester film, when the raw resin is melted, at least one of the enoneimine compound and the carbodiimide compound may be added.

The carbodiimide compound or the keteneimine compound can be directly charged into the extruder, but from the viewpoint of extrusion stability, it is preferable to form a polyester and a masterbatch in advance and charge them into the extruder. When extruding using a masterbatch containing a keteneimine compound, it is preferable to give a variation to the supply amount of the masterbatch containing a keteneimine compound. Furthermore, the enoneimine compound in the masterbatch is preferably concentrated. From the viewpoint of cost, the concentration ratio is preferably 2 times to 100 times the concentration in the film after film formation, and more preferably 5 times to 50 times.

Furthermore, the melt extruded from the extruder is cast on a casting drum after passing through a gear pump, a filter, and a multi-layer mold. For the multi-layer mold method, either a multi-manifold mold or a feed-block mold can be suitably used. The shape of the mold may be any of a T-shaped mold, a hanger coat mold, and a fish tail type. It is preferable to impart a temperature variation to the tip (die lip) of this type of mold. On the casting drum, the melt can be brought into close contact with the cooling roll by the electrostatic application method. At this time, it is preferable to give a variation to the driving speed of the casting drum. The surface temperature of the casting drum can be approximately 10°C to 40°C. The diameter of the casting drum is preferably 0.5 m or more and 5 m or less, more preferably 1 m or more and 4 m or less. The driving speed of the casting drum (the linear speed of the outermost circumference) is preferably 1 m/min or more and 50 m/min or less, and more preferably 3 m/min or more and 30 m/min or less.

In the manufacturing method of the laminated polyester film, the unstretched polyester film formed is subjected to a stretching treatment. The extension is carried out in one of the vertical (MD: Machine Direction) and the horizontal (TD: Transverse Direction) directions. The extension treatment may be either MD extension or TD extension. The stretching treatment is preferably performed at the glass temperature of the polyester film (Tg: unit°C) or higher and Tg+60°C or higher, more preferably Tg+3°C or higher, Tg+40°C or lower, and still more preferably Tg+5°C Above and below Tg+30℃. In the stretching treatment, it is preferable to impart a temperature distribution to the polyester film.

The preferred stretching ratio in the stretching treatment is 270% to 500%, more preferably 280% to 480%, and still more preferably 290% to 460%. The stretch magnification mentioned here is obtained using the following formula. Extension ratio (%)=100×{(length after extension)/(length before extension)}

After the above steps, a polyester film stretched in the first direction is obtained.

(Step of applying the composition for forming a primer layer) The manufacturing method of the laminated polyester film includes the step of applying the composition for forming an undercoat layer to one surface of the polyester film stretched in the first direction. Coating is preferable from the viewpoint that it is simple and can form a thin film with high uniformity. As the coating method, for example, a known method using a gravure coater, a bar coater, or the like can be used. As a solvent of the composition for forming an undercoat layer to be applied, water may be used, or an organic solvent such as toluene or methyl ethyl ketone may be used. One kind of solvent may be used alone, or two or more kinds may be mixed for use. The application of the composition for forming an undercoat layer on the polyester film stretched in the first direction is performed in-line following the step of stretching the unstretched polyester film in the first direction. .

Before applying the primer layer forming composition, corona discharge treatment, glow treatment, atmospheric pressure slurry treatment, flame treatment, ultraviolet (Ultraviolet, UV) treatment, etc. are performed on the polyester film stretched in the first direction. The surface treatment is also better.

It is preferable to provide a step of drying the coating film after applying the composition for forming an undercoat layer. The drying step is a step of supplying dry wind to the coating film. The average wind speed of the drying wind is preferably 5 m/sec to 30 m/sec, more preferably 7 m/sec to 25 m/sec, and still more preferably 9 m/sec to 20 m/sec or less. The drying of the coating film preferably also serves as a heat treatment.

(Extend in the second direction) The manufacturing method of the laminated polyester film includes forming a polyester film coated with a composition for forming a primer layer at least (a primer layer is coated on a polyester film obtained by uniaxially stretching an unstretched polyester film) The polyester film made of the composition) is further extended along the film surface in a second direction orthogonal to the first direction to form an undercoat layer having an elastic modulus of 0.7 GPa or more. By stretching in the second direction, the polyester film stretched in the first direction is stretched together with the undercoat layer forming composition to obtain a biaxially stretched polyester film coated with an undercoat layer . As long as it is a direction orthogonal to the first direction, the extension can be performed in either the longitudinal direction (MD) or the transverse direction (TD).

As a preferable aspect of the step of stretching in the second direction, it is the same as the step of stretching the unstretched polyester film in the first direction.

(Heat fixing step) The manufacturing method of a laminated polyester film includes the heat-fixing process which heat-fixes the polyester film with which an undercoat layer was formed at 165 degreeC or more and 215 degreeC or less. The so-called heat-fixing step refers to applying the film at 165°C or higher and 215°C or lower (preferably 175°C or higher and 205°C or lower, more preferably 185°C or higher and 190°C or lower) for 1 second to 60 seconds (more preferably 2 seconds to 30 seconds) of the heat treatment step. The heat fixation temperature in the heat fixation step determines the minute peak temperature of the biaxially stretched polyester film derived from the heat fixation temperature measured by differential scanning calorimetry (DSC). That is, if the heat-fixing temperature is 165°C or higher, the crystallinity of the polyester film is high, and the weather resistance when it is made into a laminated polyester film is excellent. In addition, if the heat-fixing temperature is 215°C or less, the polyester film has a well-aligned molecule, and therefore, it has excellent weather resistance when it is made into a laminated polyester film. The heat-fixing temperature mentioned here refers to the film surface temperature during the heat-fixing treatment. In the heat fixing step provided after the stretching step, a part of the volatile basic compound having a boiling point of 200° C. or less can be volatilized. For example, in the case where the extension in the second direction is the lateral extension, the heat fixing step is preferably followed by the lateral extension and performed in a state of being held in the chuck in the tenter. At this time, the interval between the chucks can be The width at the end of the lateral stretching is performed, and further, the interval may be enlarged, or the interval may be reduced. By applying heat fixation treatment, crystallites can be generated, and mechanical properties or durability can be improved.

The manufacturing method of the laminated polyester film is preferably to perform a heat relaxation step immediately after the heat fixing step. The heat relaxation step refers to a step of performing a process of heating the biaxially stretched polyester film in order to relax the stress to shrink the biaxially stretched polyester film. The heat relaxation step is preferably to perform relaxation in at least one of the longitudinal direction and the transverse direction, and the amount of relaxation is preferably 1% to 15% in both longitudinal and transverse directions (ratio relative to the width after transverse stretching), more preferably 2% to 10% , And more preferably 3% to 8%. The relaxation temperature in the heat relaxation step is preferably Tg+50℃～Tg+180℃ of the polyester film, more preferably Tg+60℃～Tg+150℃, and still more preferably Tg+70℃～Tg+140℃ .

When the melting point of the biaxially stretched polyester film is set to Tm, the heat relaxation step is preferably to perform a heat relaxation treatment at Tm-100°C to Tm-10°C, more preferably Tm-80°C to Tm-20°C, Even more preferably, it is Tm-70°C to Tm-35°C. The heat relaxation treatment in the heat relaxation step promotes the formation of crystallization of the biaxially stretched polyester film, and improves the mechanical strength and heat shrinkability. Furthermore, the hydrolysis resistance of the biaxially stretched polyester film is improved by the heat relaxation treatment at Tm-35°C or less. The reason is to increase the tension (binding) without disturbing the alignment of the amorphous parts that are prone to hydrolysis, thereby suppressing the reactivity with water.

The lateral relaxation can be performed by reducing the width of the clamp of the tenter. In addition, the relaxation in the longitudinal direction can be performed by narrowing the interval between adjacent clamps of the tenter. As a method of reducing the interval between adjacent jigs, a method of connecting adjacent jigs in a pantograph shape and reducing the pantograph can be cited. In addition, after the biaxially stretched polyester film is taken out from the tenter, it may be relieved by heat treatment while being conveyed under low tension. On the unit cross-sectional area of the biaxially stretched polyester film, the tension is preferably 0 N/mm ² ～0.8 N/mm ² , more preferably 0 N/mm ² ～0.6 N/mm ² , and even more preferably 0 N /mm ² ～0.4 N/mm ² . Tension of 0 N/mm ² can be achieved by installing two or more pairs of nip rollers during conveyance, and slackening (dangling) between the two or more pairs of nip rollers.

The biaxially stretched polyester film taken out from the tenter is preferably trimmed at both ends held by the clamp, and then rolled up after performing knurling processing (embossing processing) on both ends. The preferred width of the biaxially stretched polyester film is 0.8 m to 10 m, more preferably 1 m to 6 m, and still more preferably 1.5 m to 4 m. The thickness of the biaxially stretched polyester film is preferably 30 μm to 300 μm, more preferably 40 μm to 280 μm, and still more preferably 45 μm to 260 μm. The adjustment of the thickness of the biaxially stretched polyester film can be achieved by the adjustment of the ejection amount of the extruder or the adjustment of the film production speed (the adjustment of the speed of the cooling roll, the stretching speed in conjunction with it, etc.).

Recycling films such as the edge portion of the trimmed biaxially stretched polyester film are recovered as a resin mixture and reused. The recycled film becomes the raw material of the laminated polyester film of the next batch, and it returns to the drying step as described above and repeats the manufacturing step sequentially.

＜Protection sheet for solar cell＞ The protective sheet for solar cells has the laminated polyester film described above. Therefore, the protective sheet for solar cells can coexist the cohesion resistance and weather resistance (humid heat stability). In addition, the protective sheet for solar cells may have at least one functional layer such as a resin layer or a weather resistance layer as necessary.

The protective sheet for solar cells may be coated with the following functional layer on a biaxially stretched laminated polyester film, for example. For the coating setting of the functional layer, known coating techniques such as roll coating, knife edge coating, gravure coating, curtain coating and the like can be used. In addition, surface treatment (flame treatment, corona treatment, plasma treatment, ultraviolet treatment, etc.) may be performed on the laminated polyester film before the application and installation of these functional layers. Furthermore, it is also preferable to bond the laminated polyester film and the functional layer using an adhesive.

[Resin layer] The protective sheet for a solar cell preferably has the above-mentioned laminated polyester film and an acrylic resin-containing resin layer arranged on the undercoat layer of the laminated polyester film. The resin layer may have a single-layer structure or a multilayer structure of two or more layers. When the resin layer has a laminated structure of two or more layers, for example, it is preferable to include the following resin layer (B) and resin layer (C).

(Resin layer (B)) It is more preferable to laminate the resin layer (B) on the surface of the laminated polyester film on which the primer layer is laminated on the protective sheet for solar cells. As a method of laminating the resin layer (B), the following form is preferred: a solution obtained by dissolving the resin component in the resin layer (B) in an appropriate solvent, or a dispersion obtained by dispersing the resin component in water The body is applied as a composition for forming a resin layer (B) and laminated.

The resin component in the resin layer (B) preferably contains at least an acrylic resin, and other resins such as acrylic resin and polyolefin resin, polyurethane resin, and polyester resin may be used in combination. The resin component in the resin layer (B) can use commercially available products, such as AS-563A (manufactured by Daicel Fine Chemical Co., Ltd.), Julimer (registered trademark) ET-410, Julimer SEK-301 (all manufactured by Japan Pure Chemical Industries Co., Ltd.), Bonron (registered trademark) XPS001, Bonron (registered trademark) XPS002 (all manufactured by Mitsui Chemicals Co., Ltd.) ) And other acrylic resins, Alowbase (registered trademark) SE-1013N, SD-1010, TC-4010, TD-4010 (all manufactured by Unigene), Hytec S3148, S3121, S8512 (all manufactured by Toho Chemical Co., Ltd.), Chemipearl (registered trademark) S-120, S-75N, V100, EV210H (all manufactured by Mitsui Chemicals Co., Ltd.) and other polyolefins Resin etc. The resin component in the resin layer (B) may be used alone or in combination of two or more, but the content of the acrylic resin is preferably 50% by mass or more of the total mass of the resin components in the resin layer (B) .

The composition for forming the resin layer (B) may contain other additives as necessary in addition to the resin component and the solvent or dispersion medium.

-Other additives- As other additives, corresponding to the function imparted to the resin layer (B), for example, inorganic particles to increase the strength of the film, crosslinking agents, surfactants, colorants, and ultraviolet rays to increase the uniformity of the coating film Absorbents, antioxidants, preservatives, etc.

-Inorganic particles- The resin layer (B) preferably contains inorganic particles. Examples of inorganic particles include silica particles such as colloidal silica, metal oxide particles such as titanium dioxide, aluminum oxide, zirconium oxide, magnesium oxide, and tin oxide, inorganic carbonate particles such as calcium carbonate and magnesium carbonate, and barium sulfate. And other metal compound particles, black pigment particles such as carbon black. Among them, metal oxide particles and black pigment particles are preferred, and colloidal silica, titania, alumina, zirconia, and carbon black are more preferred. Furthermore, the metal oxide particles listed above are white particles and therefore can be used as white pigments. The resin layer (B) may contain only one kind of inorganic particles, or two or more kinds. When two or more are contained, only two or more white pigments may be contained, or two or more black pigments may be contained, or white pigments and black pigments may be contained.

By using black pigments as inorganic particles, the protective sheet for solar cells can be concealed. In the solar cell, from the standpoint of ingenuity, it is preferable that the wiring for the power generation element is not visible from the outside, and it is preferable that the protective sheet for the solar cell has high concealability. Previously, in order to improve the concealment of the solar cell protective sheet, carbon black as a black pigment was directly added to the base material. However, if carbon black is directly added to the substrate, the carbon black becomes the nucleus of the crystallization of the polyester, and the crystallization speed of the polyester becomes faster. Therefore, there are problems such as difficulty in forming the film by stretching or When the film using polyester is placed in a hot and humid environment, the degree of crystallinity of the film increases rapidly, embrittlement prematurely, and the humidity and heat resistance of the film decreases. On the other hand, in one embodiment of the present invention, black pigments such as carbon black are added to the resin layer (B), thereby not only improving the craftsmanship and film strength, but also suppressing biaxial substrates. The damp and heat resistance of the stretched polyester film is reduced, and furthermore, the advantage of high concealability can be imparted to the protective sheet for solar cells.

The colloidal silica that can be used in the resin layer (B) refers to a form in which particles containing silicon oxide as a main component use water, alcohols, glycols, etc., or a mixture of these as a dispersion medium, in a colloidal state. The volume average particle diameter of colloidal silica is preferably about several nm to 100 nm. The volume average particle size can be measured by Microtrac FRA manufactured by Honeywell. The particle shape of colloidal silica can be spherical, or the spherical particles can be connected to form a rosary shape.

Colloidal silica can be used commercially available products, such as: Snowtex (registered trademark) series manufactured by Nissan Chemical Industry Co., Ltd., and Cutler (registered trademark) manufactured by Nissan Chemical Industry Co., Ltd. Cataloid) (registered trademark)-S series, Bayer's Levasil series, etc. Specifically, for example, there are: Snowtex (registered trademark) ST-20, ST-30, ST-40, ST-C, ST-N, ST-20L, manufactured by Nissan Chemical Industry Co., Ltd. ST-O, ST-OL, ST-S, ST-XS, ST-XL, ST-YL, ST-ZL, ST-OZL, ST-AK, Snowtex (registered trademark) AK series, Snowtex (registered trademark) PS series, Snowtex (registered trademark) UP series, etc.

The carbon black used in the resin layer (B) is not particularly limited, and carbon black known as a black pigment can be appropriately selected and used. As the carbon black, in order to obtain high tinting power in a small amount, it is preferable to use carbon black particles, more preferably to use carbon black particles having a volume average particle diameter of 1 μm or less, and still more preferably a volume average particle diameter of 0.1 μm to 0.8 μm carbon black particles. Furthermore, the volume average particle size can be measured by the method already described. In addition, the carbon black particles are preferably dispersed in water together with a dispersant for use. As the carbon black, commercially available products that are already on the market can be used, for example, MF-5630 Black (manufactured by Dainichi Seika Co., Ltd.), or the one described in paragraph [0035] of Japanese Patent Laid-Open No. 2009-132887 Wait.

The volume average particle diameter of the inorganic particles contained in the resin layer (B) is not particularly limited, but from the viewpoint of enhancing the film strength and maintaining good adhesiveness, the volume average particle diameter is preferably the resin layer (B ) Or less, more preferably 1/2 or less of the film thickness of the resin layer (B), and still more preferably 1/3 or less of the film thickness of the resin layer (B).

The content rate of the inorganic particles in the resin layer (B) is preferably in the range of 10% by volume to 35% by volume, and more preferably in the range of 20% by volume to 30% by volume.

-Crosslinking agent- The resin component contained in the resin layer (B) can form a crosslinked structure by a crosslinking agent. That is, the resin layer (B) may contain a crosslinking agent. By forming a cross-linked structure in the resin layer (B), the adhesiveness with the adjacent layer can be further improved, which is preferable. As a crosslinking agent, an epoxy type crosslinking agent, an isocyanate type crosslinking agent, a melamine type crosslinking agent, a carbodiimide type crosslinking agent, an oxazoline type crosslinking agent etc. are mentioned, for example. As a specific example of a crosslinking agent, the same crosslinking agent as the crosslinking agent which can be used for a primer layer can be mentioned, and a preferable form is also the same.

-Catalyst of crosslinking agent- When the resin layer (B) contains a crosslinking agent, it may further contain a catalyst for the crosslinking agent. When the resin layer (B) contains the catalyst of the crosslinking agent, the crosslinking reaction between the resin component and the crosslinking agent is promoted, and the solvent resistance of the resin layer (B) can be improved. In addition, as the crosslinking reaction proceeds well, the adhesion between the resin layer (B) and the primer layer, or the resin layer (B) and the resin layer (C) described later is further improved. In particular, when a crosslinking agent having an oxazoline group (oxazoline-based crosslinking agent) is used as the crosslinking agent, it is preferable to use a catalyst of the crosslinking agent.

As a catalyst of a crosslinking agent, an onium compound is mentioned, for example. As an onium compound, an ammonium salt, a sulfonium salt, an oxonium salt, an iodine salt, a phosphonium salt, a nitronium salt, a nitrosium salt, a diazonium salt, etc. are mentioned suitably. As a catalyst of these crosslinking agents, the catalyst of the same crosslinking agent as the catalyst of the crosslinking agent which can be used for an undercoat layer is mentioned, and a preferable form is also the same.

-The thickness of the resin layer (B)- From the viewpoint of improving adhesiveness, the thickness of the resin layer (B) is preferably thicker than the thickness of the resin layer (C) which is an easy-to-adhesive layer described later. That is, when the thickness of the resin layer (B) is set to (b) and the thickness of the resin layer (C) is set to (c), the relationship of (b)>(c) is preferable, and (b) ): (c) is the range from 2:1 to 15:1. In addition, the thickness of the resin layer (B) is preferably 0.5 μm or more, more preferably 0.7 μm or more. In addition, the thickness of the resin layer (B) is preferably 7.0 μm or less. If the thickness of the resin layer (B) and the balance between the thickness of the resin layer (B) and the thickness of the resin layer (C) are within the above range, the characteristics of the resin component forming the resin layer (B) will be well expressed. When the solar cell protective sheet is applied to the solar cell module, the adhesion between the solar cell protective sheet and the sealing material and the durability of the solar cell protective sheet become more excellent.

-Method of forming resin layer (B)- As a method of forming the resin layer (B), for example, a method of applying a composition for forming a resin layer is exemplified. Coating is preferable from the viewpoint that it is simple and can form a thin film with high uniformity. As the coating method, for example, a known method using a gravure coater, a bar coater, or the like can be used.

It is preferable to provide a step (drying step) of drying the coating film after coating the composition for forming the resin layer (B). The drying step is a step of supplying dry wind to the coating film. The average wind speed of the drying wind is preferably 5 m/sec to 30 m/sec, more preferably 7 m/sec to 25 m/sec, and still more preferably 9 m/sec to 20 m/sec or less. When the resin layer (B) is formed by coating, it is preferable to combine drying and heat treatment of the coating film in the drying step.

(Resin layer (C)) When the protective sheet for solar cells has the resin layer (B), it is preferable to have the resin layer (C) on the surface of the resin layer (B) opposite to the primer layer. The resin layer (C) is preferably a layer located at a position directly in contact with the sealing material of the solar cell module to which the solar cell protective sheet of one embodiment of the present invention is applied. That is, it is preferably a layer that is located on the outermost layer of the protective sheet for solar cells and functions as an easy-to-bond layer. The resin layer (C) contains at least a resin component, and may contain various additives as necessary.

Examples of the resin component in the resin layer (C) include one or more resins selected from acrylic resins, polyester resins, polyurethane resins, silicone compounds, and polyolefin resins. By using the resin as the resin component, the adhesion between the resin layer (C) and the adjacent layer is further improved. As a resin component, the resin shown below is mentioned, for example.

As the acrylic resin, for example, a polymer containing polymethyl methacrylate, polyethyl acrylate, and the like is preferable. As the acrylic resin, commercially available products that are already on the market can be used. Examples include AS-563A (manufactured by Daicel Fine Chemicals Co., Ltd.), Julimer (registered trademark) ET-410, and Julimer) SEK-301 (all manufactured by Japan Pure Chemical Industries (Stock)). As the polyester resin, for example, polyethylene terephthalate (PET), polyethylene-2,6-naphthalate (PEN), and the like are preferable. As the polyester resin, commercially available products that are already on the market can be used. For example, Vylonal (registered trademark) MD-1245 (manufactured by Toyobo Co., Ltd.) can be preferably used. As the polyurethane resin, for example, a carbonate-based urethane resin is preferable. For example, Superflex (registered trademark) 460 (Daiichi Kogyo Pharmaceutical Co., Ltd.) is preferably used. manufacture). As a silicone compound, the compound which has a (poly)siloxane structural unit mentioned later is preferable. As the silicone-based compound, commercially available products that are already on the market can be used, for example, Ceranate (registered trademark) WSA1060, Ceranate WSA1070 (all manufactured by Di Aison Co., Ltd.), and H7620, H7630, H7650 (all manufactured by Asahi Kasei Chemical Co., Ltd.).

As the polyolefin resin, for example, a modified polyolefin copolymer is preferable. As the polyolefin resin, commercially available products on the market can be used, for example: Alowbase (registered trademark) SE-1013N, SD-1010, TC-4010, TD-4010 (all Unijik (Manufactured by shares), Hytec S3148, S3121, S8512 (all manufactured by Toho Chemical (Stock)), Chemipearl (registered trademark) S-120, S-75N, V100, EV210H ( All are Mitsui Chemicals (manufactured by Co., Ltd.), etc. Among them, from the viewpoint of improving adhesion, it is preferable to use Alowbase (registered trademark) SE-1013N, which is a terpolymer of low-density polyethylene, acrylate, and maleic anhydride, Manufactured by Unijico (Stock).

These resins may be used alone, or two or more of them may be used in combination. When two or more of the resins are used in combination, the combination of acrylic resin and polyolefin resin, the combination of polyester resin and polyolefin resin, the combination of urethane resin and polyolefin resin are preferred, and the combination of urethane resin and polyolefin resin is more preferred. Combination of acrylic resin and polyolefin resin. That is, the protective sheet for solar cells preferably has a structure in which at least two layers are laminated, and the outermost layer contains acrylic resin and polyolefin resin.

When used in a combination of acrylic resin and polyolefin resin, the content of the acrylic resin relative to the total of the polyolefin resin and the acrylic resin in the resin layer (C) is preferably 3% by mass to 50% by mass, It is more preferably 5% by mass to 40% by mass, particularly preferably 7% by mass to 25% by mass.

-Crosslinking agent- The resin component contained in the resin layer (C) can form a crosslinked structure by a crosslinking agent. That is, the resin layer (C) may contain a crosslinking agent. By forming a cross-linked structure in the resin layer (C), the adhesiveness with the adjacent layer can be further improved, which is preferable. As a crosslinking agent, an epoxy type crosslinking agent, an isocyanate type crosslinking agent, a melamine type crosslinking agent, a carbodiimide type crosslinking agent, an oxazoline type crosslinking agent etc. are mentioned, for example. As a specific example of a crosslinking agent, the same crosslinking agent as the crosslinking agent which can be used for an undercoat layer can be mentioned. Among them, the crosslinking agent contained in the resin layer (C) is preferably an oxazoline-based crosslinking agent. Examples of the oxazoline-based crosslinking agent include: Epocros (registered trademark) K2010E, Epocros K2020E, Epocros K2030E, Epocros ) WS-500, Epocros WS-700 (all manufactured by Nippon Shokubai Chemical Industry Co., Ltd.), etc.

Only one type of crosslinking agent may be used, or two or more types may be used in combination. With respect to the resin component contained in the resin layer (C), the amount of crosslinking agent added is preferably 0.5% by mass to 50% by mass, more preferably 3% by mass to 40% by mass, and particularly preferably 5% by mass or more. Full 30% by mass. In particular, if the addition amount of the crosslinking agent is 0.5% by mass or more, a sufficient crosslinking effect can be obtained while maintaining the film strength and adhesion of the resin layer (C). If the addition amount is 50% by mass or less, the coating can be The pot life of the cloth liquid is kept long. If the addition amount is less than 40% by mass, the coating surface can be improved.

-Catalyst of crosslinking agent- When the resin layer (C) contains a crosslinking agent, it may further contain a catalyst for the crosslinking agent. When the resin layer (C) contains the catalyst of the crosslinking agent, the crosslinking reaction between the resin component and the crosslinking agent is promoted, and the solvent resistance of the resin layer (C) can be improved. In addition, the crosslinking reaction progresses well, and the adhesion between the resin layer (C) and the sealing material is further improved. In particular, when an oxazoline-based crosslinking agent is used as the crosslinking agent, it is preferable to use a catalyst of the crosslinking agent.

As a catalyst of a crosslinking agent, an onium compound is mentioned, for example. As an onium compound, an ammonium salt, a sulfonium salt, an oxonium salt, an iodine salt, a phosphonium salt, a nitronium salt, a nitrosium salt, a diazonium salt, etc. are mentioned suitably. As a catalyst of these crosslinking agents, the catalyst of the same crosslinking agent as the catalyst of the crosslinking agent which can be used for an undercoat layer is mentioned, and a preferable form is also the same.

The catalyst of the crosslinking agent may be only one type, or two or more types may be used in combination. With respect to the crosslinking agent in the resin layer (C), the addition amount of the catalyst of the crosslinking agent is preferably in the range of 0.1% by mass or more and 15% by mass or less, and more preferably 0.5% by mass or more and 12% by mass or less The range is more preferably 1% by mass or more and 10% by mass or less, and particularly preferably 2% by mass or more and 7% by mass or less. The addition amount of the catalyst of the cross-linking agent relative to the cross-linking agent is 0.1% by mass or more, which means that the catalyst containing the cross-linking agent is actively contained. The crosslinking reaction is easy to proceed, and more excellent solvent resistance can be obtained. In addition, from the viewpoint of solubility, filterability of the coating liquid, and improvement of the adhesion between the resin layer (C) and the sealing material, it is advantageous that the content of the catalyst of the crosslinking agent is 15% by mass or less.

As long as the effect produced by one embodiment of the present invention is not impaired, the resin layer (C) may contain various additives in addition to the resin component. Examples of additives include antistatic agents, ultraviolet absorbers, colorants, preservatives, and the like. Examples of the antistatic agent include surfactants such as nonionic surfactants, organic conductive materials, inorganic conductive materials, organic/inorganic composite conductive materials, and the like. As the surfactant, nonionic surfactants and anionic surfactants are preferred, and among them, nonionic surfactants are more preferred. As the nonionic surfactant, preferably, it has an ethylene glycol chain (polyoxyethylene chain; -(CH ₂ -CH ₂ -O) _n -) and does not have a carbon-carbon triple bond (alkyne bond) The non-ionic surfactant. Furthermore, as a nonionic surfactant, it is more preferable that the ethylene glycol chain is 7-30. Specific examples of nonionic surfactants include hexaethylene glycol monododecyl ether, 3,6,9,12,15-pentaoxahexadecane-1-ol, and polyoxyethylene phenyl Ether, polyoxyethylene methyl phenyl ether, polyoxyethylene naphthyl ether, polyoxyethylene methyl naphthyl ether, etc. are not limited to these nonionic surfactants. When a surfactant is used as an antistatic agent, relative to the total solid content of the resin layer (C), the content of the surfactant in the resin layer (C) is preferably 2.5% by mass to 40% by mass, more preferably 5.0 Mass% to 35% by mass, more preferably 10% to 30% by mass. Within this content range, the partial discharge voltage drop of the solar cell protective sheet is suppressed, and the solar cell protective sheet is combined with the sealing material (for example, EVA: ethylene-vinyl acetate) for the sealing material that seals the solar cell element. The adhesiveness of the ester copolymer) is well maintained.

Examples of organic conductive materials include: cationic conductive compounds having cationic substituents such as ammonium groups, amine salt groups, and quaternary ammonium groups in the molecule; and sulfonate groups, phosphate groups, and carboxylic acids. Anionic conductive compounds with anionic substituents such as bases; amphoteric conductive compounds with both anionic and cationic substituents. Plasma conductive materials; conjugated polyenes Conductive polymer compounds such as polyacetylene, polyparaphenylene, polyaniline, polythiophene, polyparaphenylene vinylene, polypyrrole, etc. of the skeleton.

Examples of inorganic conductive materials include: gold, silver, copper, platinum, silicon, boron, palladium, rhenium, vanadium, osmium, cobalt, iron, zinc, ruthenium, chromium, nickel, aluminum, tin , Zinc, titanium, tantalum, zirconium, antimony, indium, yttrium, lanthanum, magnesium, calcium, cerium, hafnium, barium and other inorganic groups as the main component of the oxidation, sub-oxidation, sub-sub-oxidation; the inorganic substance A mixture of the group and the inorganic substance group being oxidized, sub-oxidized, and sub-sub-oxidized (hereinafter referred to as inorganic oxides); the inorganic substance group is used as the main component to be nitridated, A mixture of nitriding and subnitriding; the inorganic group and the mixture of nitriding, nitriding, and subnitriding the inorganic group (hereinafter referred to as inorganic nitrogen ); the inorganic group as the main component is subjected to nitrogen oxidation, nitrous oxidation, or sub-nitrous oxidation; the inorganic group and the inorganic group are subjected to nitrogen oxidation, nitrous oxidation , Or a mixture of sub-nitrous oxides (hereinafter referred to as inorganic nitrogen oxides); those made by carbonizing, sub-carbonizing, or sub-sub-carbonizing the inorganic group as the main component; A mixture of the inorganic group and the inorganic group by carbonization, sub-carbonization, or sub-carbonization (hereinafter referred to as inorganic carbide); the inorganic group as the main component is subjected to fluorine At least one of halogenation, chlorination, bromination, and iodination is formed by halogenation, subhalogenation, or subhalogenation; the inorganic group is formed by halogenating, subhalogenating, or subhalogenating the inorganic group (Hereafter referred to as inorganic halides); the mixture of the inorganic group and the inorganic group vulcanized, sulfided, or subsulfided (hereafter referred to as inorganic halides) Sulfides); inorganic compounds doped with different elements; graphite-like carbon, diamond-like carbon, carbon fiber, carbon nanotubes, fullerenes and other carbon compounds (hereinafter referred to as carbon compounds) ; These mixtures and so on.

[Weather resistant layer] The protective sheet for solar cells may have at least one layer of the weather-resistant layer described in detail below on the surface of the laminated polyester film opposite to the side having the primer layer (the surface on the back side of the biaxially stretched polyester film). Since the solar cell protective sheet has a weather-resistant layer, the influence from the environment on the substrate is suppressed, and the weather resistance and durability are further improved. Hereinafter, as a weather-resistant layer that can be suitably used for a protective sheet for a solar cell, a coating layer (D) and a coating layer (E) are taken as examples and described in detail.

(Weather resistant layer containing binder, colorant and scattering particles: coating layer (D)) As the weather-resistant layer, a layer containing a binder, a coloring agent, and scattering particles (coating layer (D)) can be cited. In a solar cell module with a laminated structure of a solar cell side substrate [= a transparent substrate (such as a glass substrate, etc.) on the side where sunlight is incident] / an element structure portion containing solar cell elements / a solar cell protective sheet, The coating layer (D) is preferably a back surface protective layer in which the side of the substrate (biaxially stretched polyester film) arranged in the solar cell protective sheet is the opposite side to the solar cell side substrate.

The coating layer (D) may have a single-layer structure or a multilayer structure of two or more layers. In the case of a single-layer structure, it is preferable to arrange a layer containing a binder, a coloring agent, and scattering particles on the substrate. On the other hand, in the case of a two-layer or more layered structure, it is preferable to laminate two or more layers on the substrate containing the binder, colorant, and scattering particles, and not only to form an adhesive layer on the substrate. A layer containing a fluorine resin, a coloring agent, and scattering particles, and a layer containing any one of a fluorine-based resin, which is described later, and not containing a coloring agent and scattering particles (for example, the coating layer (E), which will be described in detail below). The layer of the composition).

-Binder- The adhesive used in the coating layer (D) may be any of a resin component, an inorganic polymer, and an adhesive containing a composite compound of the resin component and the inorganic polymer. When the coating layer (D) contains the above-mentioned components, the adhesion to the substrate is improved, or the adhesion between the layers is improved when the weather-resistant layer is made into a laminated structure of two or more layers, and the resistance to heat and humidity can be obtained. Degradability. The inorganic polymer is not particularly limited, and well-known inorganic polymers can be used. The resin component or composite compound is not particularly limited, but preferably contains at least one of a fluorine-based resin and a silicone-based compound, and more preferably contains at least one of a fluorine-based resin and a silicone-acrylic organic/inorganic composite compound , Especially preferably, it contains a silicone-acrylic organic/inorganic composite compound.

"Silicone Compounds" The silicone compound is a compound having a (poly)siloxane structure in the molecular chain, and is not particularly limited. The silicone compound may be a homopolymer of a compound having a (poly)siloxane structural unit, or a copolymer containing a (poly)siloxane structural unit and other structural units. Other structural units copolymerized with (poly)siloxane structural units are non-siloxane structural units.

The coating layer (D) contains a silicone compound, so that the adhesiveness of the material adjacent to the substrate of the solar cell protective sheet and the coating layer (E) described later, and the durability in a humid and hot environment are improved. Excellent.

The silicone compound is preferably one having a siloxane structural unit represented by the following general formula (1) as a (poly)siloxane structure.

通式（1）[化2]

General formula (1)

In the general formula (1), R ¹ and R ² each independently represent a hydrogen atom, a halogen atom, or a monovalent organic group. Here, R ¹ and R ² may be the same or different, and multiple R ¹ and R ² may be the same or different from each other. n represents an integer of 1 or more. The partial structure of "-(Si(R ¹ )(R ² )-O) _n -", which is the siloxane structural unit in silicone compounds, can be formed into a variety of linear, branched, or cyclic structures. (Poly)siloxane fragments of siloxane structure.

Examples of the halogen atom when R ¹ and R ² represent a halogen atom include a fluorine atom, a chlorine atom, and an iodine atom. When R ¹ and R ² represent a monovalent organic group, the monovalent organic group may be any group as long as it is a group that can be covalently bonded to a Si atom. For example, an alkyl group (for example: Methyl, ethyl, etc.), aryl (for example: phenyl, etc.), aralkyl (for example: benzyl, phenylethyl, etc.), alkoxy (for example: methoxy, ethoxy, propoxy Group, etc.), aryloxy group (for example: phenoxy group, etc.), mercapto group, amino group (for example: amino group, diethylamino group, etc.), amide group, etc. These organic groups may be unsubstituted or may further have a substituent.

Among them, from the viewpoint of adhesion to adjacent layers and durability in a humid and hot environment, as R ¹ and R ² , it is preferable that each independently is a hydrogen atom, a chlorine atom, a bromine atom, unsubstituted or Substituted C1-C4 alkyl (especially methyl, ethyl), unsubstituted or substituted phenyl, unsubstituted or substituted alkoxy, mercapto, unsubstituted amine, The amide group is more preferably an unsubstituted or substituted alkoxy group (preferably an alkoxy group having 1 to 4 carbon atoms) from the viewpoint of durability in a hot and humid environment.

n is preferably 1 to 5,000, more preferably 1 to 1,000.

Relative to the total mass of the silicone-based compound, the "-(Si(R ¹ )(R ² )-O) _n -" part of the silicone-based compound (the (poly)silicone represented by the general formula (1)) The ratio of the oxane structural unit) is preferably 15% by mass to 85% by mass. Among them, from the viewpoint of improving the film strength of the coating layer (D), suppressing damage due to scratching or rubbing, etc., and having better adhesion to adjacent layers and durability in a humid and hot environment, it is more It is preferably in the range of 20% by mass to 80% by mass. If the ratio of the (poly)siloxane structural unit is 15% by mass or more, the film strength of the coating layer (D) is improved, preventing damage due to scratches or rubbing, collisions with flying small stones, etc., and Adjacent layers have excellent adhesion. By suppressing the occurrence of damage, the weather resistance is improved, and the peeling resistance, shape stability, and durability when exposed to a humid and hot environment can be effectively improved, which is easily degraded by heat or moisture. In addition, if the ratio of the (poly)siloxane structural unit is 85% by mass or less, the coating liquid can be stably maintained.

When the silicone compound is a copolymer having a (poly)siloxane structural unit and other structural units, it is preferable to contain 15% to 85% by mass in the molecular chain by the general formula (1) The indicated (poly)siloxane structural unit contains 85% to 15% by mass of non-siloxane structural units in a mass ratio. The coating layer (D) contains this copolymer to increase the film strength of the coating layer (D) and prevent damage due to scratching or rubbing. Compared with the previous one, it can be greatly improved and adjacent The adhesiveness of the layer, that is, the peeling resistance, shape stability, and durability in a humid and hot environment that are easily degraded after being given heat or moisture.

As the copolymer, it is preferable to copolymerize a silicone compound (including polysiloxane) and a compound selected from a non-silicone-based monomer or a non-silicone-based polymer, and has the following formula (1) The block copolymer of the (poly)siloxane structural unit and the non-siloxane structural unit. In this case, the silicone compound and the non-silicone-based monomer or non-silicone-based polymer to be copolymerized may be a single type or two or more types.

Non-siloxane structural units (derived from non-siloxane monomers or non-siloxane polymers) that are copolymerized with (poly)siloxane structural units are not special except that they do not have a siloxane structure The limitation may be any of polymer fragments derived from any polymer. Examples of the polymer (precursor polymer) of the precursor of the polymer segment include various polymers such as a vinyl polymer, a polyester polymer, and a polyurethane polymer. Among them, in terms of ease of production and excellent hydrolysis resistance, vinyl-based polymers and polyurethane-based polymers are preferred, and vinyl-based polymers are particularly preferred.

As representative examples of vinyl polymers, various polymers such as acrylic polymers, vinyl carboxylate polymers, aromatic vinyl polymers, and fluoroolefin polymers can be cited. Among them, from the viewpoint of the degree of freedom of design, an acrylic polymer is particularly preferred. In addition, the polymer forming the non-siloxane structural unit may be a single type, or two or more types may be used in combination.

In addition, the precursor polymer capable of forming a non-siloxane structural unit preferably contains at least one of an acid group and a neutralized acid group, and/or a hydrolyzable silyl group. Among such precursor polymers, vinyl polymers can be prepared by various methods such as the following: (1) A vinyl monomer containing acid groups and a monomer containing hydrolyzable silyl groups and/or silanol groups can be prepared. A method of copolymerizing vinyl monomers and monomers that can be copolymerized with these monomers; (2) Making a vinyl polymer containing hydroxyl groups and hydrolyzable silyl groups and/or silanol groups prepared in advance, The method of reacting with polycarboxylic anhydride; (3) Make the pre-prepared vinyl polymer containing acid anhydride group, hydrolyzable silyl group and/or silanol group, and compound with active hydrogen (water, alcohol, amine, etc.) ) The method of reaction.

The precursor polymer can be produced, for example, by the method described in paragraph [0021] to paragraph [0078] of JP 2009-52011 A.

The coating layer (D) can use a silicone compound alone as a binder, or can be used in combination with other resin components, inorganic polymers, or composite compounds. When a silicone-based compound is used in combination with other resin components, inorganic polymers or composite compounds, the content of the silicone-based compound is preferably 30% by mass or more of the total binder amount, more preferably 60% by mass or more. With the silicone compound content of 30% by mass or more, the film strength of the coating layer (D) is improved to prevent damage due to scratching or rubbing, and the adhesion to the adjacent layer and the hot and humid environment The durability of the lower part is more excellent.

The molecular weight of the silicone compound is preferably 5,000 to 100,000, more preferably 10,000 to 50,000.

When preparing silicone compounds, the following methods can be used: (i) a method of reacting a precursor polymer with a polysiloxane having a structural unit represented by the general formula (1); (ii) polymerizing in the precursor A method of hydrolyzing and condensing a silane compound having a structural unit represented by the general formula (1) in which ^{R 1} and/or R ² are hydrolyzable groups in the presence of a compound. As the silane compound used in the method (ii), various silane compounds can be cited, but alkoxysilane compounds are particularly preferred.

When the silicone compound is prepared by the method (i), for example, if necessary, water and a catalyst are added to the mixture of the precursor polymer and polysiloxane, and the reaction is carried out at a temperature of about 20°C to 150°C. The reaction is carried out in about 30 minutes to 30 hours (preferably at 50°C to 130°C for 1 hour to 20 hours), whereby the silicone compound can be prepared. As the catalyst, various silanol condensation catalysts such as acidic compounds, basic compounds, and metal-containing compounds can be added. In addition, when the silicone compound is prepared by the method (ii), for example, water and a silanol condensation catalyst are added to the mixture of the precursor polymer and the alkoxysilane compound, and the temperature is about 20℃～150℃. Hydrolysis and condensation are carried out at a temperature for about 30 minutes to 30 hours (preferably at 50°C to 130°C for 1 hour to 20 hours), whereby the silicone compound can be prepared.

In addition, commercially available products on the market can be used as silicone-based compounds, for example: Ceranate (registered trademark) series manufactured by Di Aisheng (Co., Ltd.) (for example, Ceranate (registered trademark) WSA1070 , Cerana (Ceranate) WSA1060, etc.), H7600 series (H7650, H7630, H7620, etc.) manufactured by Asahi Kasei Chemical Co., Ltd., inorganic acrylic composite emulsion manufactured by JSR (Stock), etc.

The coating amount of the silicone compound in the coating layer (D) is preferably in the range of more than 0.2 g/m ² and 15 g/m ² or less. If the coating amount of the silicone compound is in the above-mentioned range, damage due to external force on the protective sheet for solar cells can be suppressed. In the above-mentioned range, from the viewpoint of the film strength of the coating layer (D), the range of 0.5 g/m ² to 10.0 g/m ² is preferable, and the range of 1.0 g/m ² to 5.0 g/ is more preferable. m ² range.

Among the above, the coating layer (D) is preferably made of Ceranate (registered trademark) series manufactured by Di Aison (Co., Ltd.), or inorganic and acrylic composite emulsion manufactured by JSR (Co., Ltd.) as silicone-based The form of the compound.

-Fluorine-based resin- The coating layer (D) can be composed of a fluorine-based resin as the main binder. The so-called primary adhesive means the adhesive with the largest content in the layer. The fluorine-based resin that can be used here ^{is not particularly limited as long as it has a repeating unit represented by -(CFX 1} -CX ² X ³ )- (wherein, X ¹ , X ² , and X ³ are each Independently represents a hydrogen atom, a fluorine atom, a chlorine atom, or a perfluoroalkyl group having 1 to 3 carbon atoms). Specific examples include: polytetrafluoroethylene (hereafter, sometimes referred to as PTFE (Polytetrafluoroethylene)), polyvinyl fluoride (hereafter, sometimes referred to as PVF (Polyvinyl fluoride)), polyvinylidene fluoride (hereafter, there are When expressed as PVDF (Poly (vinylidene difluoride)), polychlorotrifluoroethylene (hereinafter, sometimes expressed as PCTFE (Polychlorotrifluoroethylene)), polytetrafluoropropylene (hereinafter, sometimes expressed as PTFP (Tetrafluoropropene)), etc.

The fluorine-based resin may be a homopolymer obtained by polymerizing a single monomer, or a copolymer obtained by copolymerizing two or more monomers. Examples of copolymers obtained by copolymerizing two or more monomers include copolymers obtained by copolymerizing tetrafluoroethylene and tetrafluoropropylene (abbreviated as P(TFE/TPP)), and tetrafluoroethylene Copolymers (abbreviated as P(TFE/VDF)) etc. which are copolymerized with vinylidene fluoride. Furthermore, as the fluorine-based resin, a copolymer obtained by copolymerizing a fluorine-based structural unit represented ^{by -(CFX 1} -CX ² X ^{3 )- and other structural units may be used.} Examples of these include: copolymers of tetrafluoroethylene and ethylene (hereinafter abbreviated as P(TFE/E)), copolymers of tetrafluoroethylene and propylene (abbreviated as P(TFE/P)), tetrafluoroethylene and ethylene Copolymer of vinyl fluoride and vinyl ether (abbreviated as P (TFE/VE)), copolymer of tetrafluoroethylene and perfluorovinyl ether (abbreviated as P (TFE/FVE)), chlorotrifluoroethylene and vinyl Ether copolymer (abbreviated as P(CTFE/VE)), copolymer of chlorotrifluoroethylene and perfluorovinyl ether (abbreviated as P(CTFE/FVE)).

These fluorine-based resins can be used by dissolving the resin in an organic solvent, or can be used by dispersing the resin in water. From the viewpoint that the environmental load is small, the latter is preferable. Regarding the aqueous dispersion of fluorine-based resin, for example, Japanese Patent Laid-Open No. 2003-231722, Japanese Patent Laid-Open No. 2002-20409, and Japanese Patent Laid-Open No. 9-194538 can be referred to, and the above-mentioned can be applied. Resins described in each gazette.

As the binder of the coating layer (D), the fluorine-based resin may be used alone, or two or more of them may be used in combination. In addition, when a fluorine-based resin is used as the main binder of the coating layer (D), acrylic resin, polyester resin, and polyurethane can also be used in combination within a range not exceeding 50% by mass of all the binders. Resins other than fluorine resins such as ester resins, polyolefin resins, and silicone compounds.

The content of the binder (including the silicone compound) in the coating layer (D) is preferably in the range of 15 parts by mass to 200 parts by mass relative to 100 parts by mass of the scattering particles described below, more preferably 17 parts by mass to 100 The range of parts by mass. If the content of the binder is 15 parts by mass or more, the strength of the colored layer can be sufficiently obtained, and if it is 200 parts by mass or less, the reflectance and decorativeness can be maintained well.

-Colorant- The coloring agent that can be used for the coating layer (D) is not particularly limited, and a known dye or a known pigment can be used. However, the coloring agent in this specification does not include the scattering particles described later. Examples of the coloring agent include black coloring agents, green coloring agents, blue coloring agents, and red coloring agents.

The coloring agent that can be used for the coating layer (D) preferably contains at least one selected from the group consisting of carbon black, titanium black, black composite metal oxides, cyanine-based pigments, and quinacridone-based pigments. In addition, the colorant can be selected according to the required optical density. Examples of black composite metal oxides include composite metal oxides containing at least one of iron, manganese, cobalt, chromium, copper, and nickel, preferably containing cobalt, chromium, iron, manganese, copper, and nickel. Two or more kinds, more preferably a color index (color index) selected from at least one or more pigments selected from PBk26, PBk27, PBk28, and PBr34. Furthermore, the pigment of PBk26 is a composite oxide of iron, manganese, and copper, the pigment of PBk27 is a composite oxide of iron, cobalt, and chromium, PBk-28 is a composite oxide of copper, chromium, and manganese, and PBr34 is a composite oxide of copper, chromium, and manganese. Composite oxide of nickel and iron. Examples of cyanine-based pigments and quinacridone-based pigments include cyanine green, cyanine blue, quinacridone red, phthalocyanine blue, and phthalocyanine green.

Among them, it is preferable to use carbon black as a coloring agent from the viewpoint that the optical density can be easily adjusted to the above-mentioned preferable range and the optical density can be adjusted in a small amount. The carbon black is preferably carbon black fine particles having a volume average particle diameter of 0.1 μm to 0.8 μm. Furthermore, the volume average particle size can be measured by the method already described. Furthermore, it is preferable to disperse carbon black together with a dispersant in water for use. Furthermore, as carbon black, commercially available products that are already on the market can be used. For example, MF-5630 Black (manufactured by Dainichi Seika Co., Ltd.) or the one described in paragraph [0035] of JP 2009-132887 can be used. Wait.

-Scattering particles- The scattering particles that can be contained in the coating layer (D) are not particularly limited, and well-known scattering particles can be used. The scattering particles refer to particles that hardly absorb light in the visible light region, and do not include the colorant. As the scattering particles, it is preferable to use a white pigment. Examples of white pigments that can be used as scattering particles include inorganic pigments such as titanium dioxide, barium sulfate, silica, alumina, magnesium oxide, calcium carbonate, kaolin, talc, colloidal silica, and organic pigments such as hollow particles. Among them, Preferably it is titanium dioxide. The crystal system of titanium dioxide includes rutile type, anatase type, and brookite type, preferably rutile type. Titanium dioxide can be _{surface treated with aluminum oxide (Al 2} O ₃ ), silicon dioxide (SiO ₂ ), alkanolamine compounds, silicon compounds, etc., if necessary. In particular, by using titanium dioxide with a bulk specific gravity of 0.50 g/cm ³ or more, the titanium dioxide is densely packed, and the film strength of the coating layer (D) is improved. On the other hand, by using titanium dioxide having a bulk specific gravity of 0.85 g/cm ³ or less, the dispersibility of titanium dioxide can be maintained well, and the surface shape of the coating layer (D) is excellent. The bulk specific gravity of the titanium dioxide used for the coating layer (D) is particularly preferably 0.60 g/cm ³ or more and 0.80 g/cm ³ or less.

The body specific gravity is the value measured by the following method. (1) Pass the colorant through a sieve with an aperture of 1.0 mm. (2) Weigh about 100 g of the colorant (m), and slowly put it into a 250 mL graduated cylinder. If necessary, after adding the colorant, carefully flatten the upper surface without compacting, and measure the volume (V). (3) According to the following formula, find the specific gravity of the body. Specific gravity=m/V (unit: g/cm ³ )

The coating layer (D) contains white pigments as scattering particles in addition to the adhesives such as silicone compounds or fluorine resins, which can increase the reflectivity of the coating layer (D) and reduce long-term high temperature and high temperature. Yellowing under wet test (2000 hours to 3000 hours at 85°C and 85% relative humidity) and ultraviolet (UV) irradiation test (according to the UV test of IEC61215, the total exposure is 45 Kwh/m ² ). Furthermore, by adding scattering particles to the coating layer (D), the adhesion to other adjacent layers is further improved. The content when the scattering particles are used for the coating layer (D) is preferably 1.0 g/m ² to 15 g/m ² per coating layer (D). If the content of the scattering particles (preferably white pigment) is 1.0 g/m ² or more, the reflectance or UV resistance (light resistance) can be effectively imparted. In addition, if the content of the scattering particles (preferably white pigment) in the coating layer (D) is 15 g/m ² or less, the surface shape of the coating layer (D) is easily maintained and the film strength is more excellent . Among them, the content of the scattering particles contained in the coating layer (D) is more preferably in the range of 2.5 g/m ² to 10 g/m ² , particularly preferably in the range of 4.5 g/m ² to 8.5 g/m ² . The volume average particle diameter of the scattering particles is preferably 0.03 μm to 0.8 μm, more preferably 0.15 μm to 0.5 μm. If the volume average particle diameter is within the range, the reflectance of light is high. The volume average particle size can be measured by the method already described.

-Other ingredients- When the protective sheet for solar cells has a coating layer (D) containing a binder, a coloring agent, and scattering particles, it may further contain various additives and other components as necessary, for example, a crosslinking agent, a surfactant, a filler, and the like. Among them, from the viewpoint of further improving the film strength and durability of the coating layer (D), it is preferable to add a crosslinking agent to form the crosslinking derived from the binder and the crosslinking agent in the coating layer (D) structure. Examples of the crosslinking agent include crosslinking agents such as epoxy-based crosslinking agents, isocyanate-based crosslinking agents, melamine-based crosslinking agents, carbodiimide-based crosslinking agents, and oxazoline-based crosslinking agents. Among them, the crosslinking agent is preferably at least one crosslinking agent selected from the group consisting of carbodiimide-based crosslinking agents, oxazoline-based crosslinking agents, and isocyanate-based crosslinking agents. As a specific example of the crosslinking agent, the one described in the undercoat layer can also be applied to the coating layer (D) in the same way, and the preferred examples are also the same.

With respect to 100 parts by mass of the adhesive contained in the coating layer (D), the amount of the crosslinking agent used in the coating layer (D) is preferably 0.5 to 30 parts by mass, more preferably 3 parts by mass Part or more but less than 15 parts by mass. If the addition amount of the crosslinking agent is 0.5 parts by mass or more, the film strength of the coating layer (D) and the adhesion to the adjacent layer will be maintained while obtaining a sufficient crosslinking effect. If it is 30 parts by mass or less, then The pot life of the coating liquid can be kept long, and if it is less than 15 parts by mass, the coating surface can be further improved.

As the surfactant that can be used for the coating layer (D), well-known surfactants such as anionic surfactants and nonionic surfactants can be cited. The addition amount of the surfactant when used in the coating layer (D) is preferably 0.1 mg/m ² to 10 mg/m ² , more preferably 0.5 mg/m ² to 3 mg/m ² . If the addition amount of the surfactant is 0.1 mg/m ² or more, a layer in which the occurrence of sinking is suppressed can be obtained, and if the addition amount is 10 mg/m ² or less, the adhesiveness with the adjacent layer is excellent. Fillers can also be added to the coating layer (D). As the filler, known fillers such as colloidal silica can be used.

The coating layer (D) can be formed by applying a coating liquid (composition for forming the coating layer (D)) containing a binder or the like on the back side of the substrate (the laminated polyester film and the one with the primer layer). The surface on the opposite side) is formed by drying. In the protective sheet for solar cells, it is preferable that the coating layer (D) is a layer formed by coating a coating layer (D) forming composition containing at least one of a silicone-based compound and a fluorine-based resin. Coating is preferable from the viewpoint that it is simple and can form a thin film with high uniformity. As the coating method, for example, a known method using a gravure coater, a bar coater, or the like can be used. As a solvent of the composition for forming the coating layer (D) to be applied, water may be used, or an organic solvent such as toluene or methyl ethyl ketone may be used. One kind of solvent may be used alone, or two or more kinds may be mixed for use. From the viewpoint of environmental load, it is preferable to use water as a solvent. When water is used as a solvent, water and an organic solvent may be used in combination. The content of water in the solvent is preferably 60% by mass or more, and more preferably 80% by mass or more relative to the total mass of the solvent. The composition for forming the coating layer (D) is preferably in the form of preparing an aqueous dispersion in which a binder or other components used in combination as necessary are dispersed in water, and the aqueous dispersion is used as the coating layer (D ) The composition for forming is applied to a desired substrate.

It is preferable to provide a step of drying the coating film after coating the composition for forming the coating layer (D). The drying temperature in the drying step may be appropriately selected in accordance with the composition of the coating liquid, the coating amount, and the like. In addition, the application to the substrate may be performed on a biaxially stretched polyester film, may be performed on a polyester film stretched in the first direction, or may be performed on an unstretched polyester film.

-The thickness of the coating layer (D)- The thickness of the coating layer (D) is generally preferably 1 μm to 30 μm, more preferably 5 μm to 25 μm, and still more preferably 10 μm to 20 μm. When the thickness is within the range and exposed to a hot and humid environment, it is difficult for moisture to penetrate into the coating layer (D). In addition, it is difficult for moisture to reach the interface between the coating layer (D) and the substrate, thereby significantly improving the adhesion And the film strength of the coating layer (D) itself is also well maintained. When exposed to a humid and hot environment, it is difficult to cause damage to the weather resistant layer.

(Weather resistant layer containing fluorine-based resin: coating layer (E)) The protective sheet for solar cells may further have a coating layer (E) containing a fluorine-based resin on the surface of the coating layer (D). When the protective sheet for solar cells has a coating layer (E) containing a fluorine-based resin, the coating layer (E) is preferably directly provided on the surface of the coating layer (D) arbitrarily provided on the substrate. The coating layer (E) is preferably located on the outermost layer of the protective sheet for solar cells. That is, the weather-resistant layer preferably has a structure in which two layers are laminated, and the weather-resistant layer furthest from the laminated polyester film contains a fluorine-based resin. The coating layer (E) containing a fluorine-based resin is preferably composed of a fluorine-based resin as a main binder. The so-called primary adhesive refers to the adhesive with the largest content in the coating layer (E). Hereinafter, the fluorine-based polymer contained in the coating layer (E) and the coating layer (E) will be specifically described.

-Fluorine-based resin- As the fluorine-based resin, there are ^{no particular restrictions as long as it has a repeating unit represented by -(CFX 1 -CX 2} X ³ )- (where X ¹ , X ² , and X ³ each independently represents a hydrogen atom, a fluorine atom, a chlorine atom, or a perfluoroalkyl group having 1 to 3 carbons). Examples of the fluorine-based resin include the same resins as the fluorine-based resin that can be used for the coating layer (D), and specific examples and preferred examples are also the same.

The fluorine-based resin may be used by dissolving the resin in an organic solvent, or may be used by dispersing resin particles in an appropriate dispersion medium such as water. From the viewpoint of a small environmental load, it is preferably used as a resin particle dispersion using water or an aqueous solvent as a dispersion medium. Regarding the aqueous dispersion of fluorine resin, for example, Japanese Patent Laid-Open No. 2003-231722, Japanese Patent Laid-Open No. 2002-20409, and Japanese Patent Laid-Open No. 9-194538 can be referred to. Used for the formation of coating layer (E).

As the binder of the coating layer (E), a fluorine-based resin may be used alone, or two or more resin components may be used in combination. When two or more resin components are used in combination, acrylic resins, polyester resins, polyurethane resins, polyolefin resins, and silicone compounds can also be used in combination within a range not exceeding 50% by mass of all adhesives. Resins other than fluorine-based resins. However, by containing more than 50% by mass of the fluorine-based resin in the coating layer (E), the effect of improving the weather resistance appears more satisfactorily.

-Lubricant- The coating layer (E) preferably contains at least one lubricant. By containing a lubricant, it is possible to suppress the decrease in sliding properties (that is, the increase in the coefficient of dynamic friction) that is likely to occur when using fluorine-based resins, so it drastically alleviates the susceptibility to external forces such as scratches or rubbing, collisions with small stones, etc. Damaging. In addition, it is possible to improve the surface depression of the coating liquid that is likely to occur when a fluorine-based resin is used, and it is possible to form a coating layer (E) with a good surface shape.

The coating layer (E) preferably contains a lubricant in the range of ^{0.2 mg/m 2} to 200 mg/m ^2. If the content of the lubricant is 0.2 mg/m ² or more, the effect of reducing the coefficient of dynamic friction is large. In addition, when the content of the lubricant is 200 mg/m ² or less, when the coating layer (E) is formed by coating, the generation of coating unevenness or agglomerates is suppressed, and the generation of sinking is suppressed. In the above range, the content of the lubricant is preferably in the range of 1.0 mg/m ² to 1150 mg/m ² from the viewpoint of the effect of reducing the coefficient of dynamic friction and coating adaptability, and more preferably 5.0 mg/m ² ～100 mg/m ² range.

Examples of lubricants include synthetic wax-based compounds, natural wax-based compounds, surfactant-based compounds, inorganic-based compounds, and organic resin-based compounds. Among them, from the viewpoint of the surface strength of the coating layer (E), a compound selected from a synthetic wax-based compound, a natural wax-based compound, and a surfactant is preferred.

Examples of synthetic wax compounds include olefin waxes such as polyethylene wax and polypropylene wax, and esters such as stearic acid, oleic acid, erucic acid, lauric acid, behenic acid, palmitic acid, and adipic acid. Amide, bisamide, ketones, metal salts and their derivatives, Fischer-tropsch wax and other synthetic hydrocarbon waxes, phosphate esters, hardened castor oil, hydrogenated waxes of hardened castor oil derivatives, etc.

Examples of natural wax compounds include plant waxes such as palm wax, candelilla wax and wood wax; petroleum waxes such as paraffin wax and microcrystalline wax; mineral waxes such as montan wax; beeswax and lanolin. And other animals are wax and so on.

Examples of surfactants include cationic surfactants such as alkyl amine salts, anionic surfactants such as alkyl sulfate ester salts, nonionic surfactants such as polyoxyethylene alkyl ethers, and alkyl betaines. And other amphoteric surfactants, fluorine surfactants, etc.

Lubricants can be used commercially available products, specifically, As synthetic wax compounds, for example, Chemipearl (registered trademark) series manufactured by Mitsui Chemicals Co., Ltd. (for example, Chemipearl (registered trademark) W700, Chemipearl W900, and Mipa (Chemipearl W950, etc.), Polyron P-502, Hymicron L-271, and Hidorin L-536 manufactured by Zhongjing Oils & Fats Co., Ltd., etc., As a natural wax compound, for example, Hyderin (Hidorin) L-703-35, Serozol (Serozol) 524, (Serozol) R-586, etc. manufactured by Chukyo Oil & Fat Co., Ltd. can be cited. In addition, Examples of surfactants include: NIKKOL (registered trademark) series manufactured by Nikko Chemicals (Co., Ltd.) (for example, NIKKOL (registered trademark) SCS, etc.), and Ai Emal (registered trademark) series (e.g. Emal (registered trademark) 40, etc.).

-Other additives- In the coating layer (E), colloidal silica, silane coupling agent, crosslinking agent, surfactant, etc. can also be added as necessary. As the colloidal silica, the same colloidal silica as the colloidal silica that can be used for the resin layer (B) can be cited, and the preferred form is also the same.

As the content when the coating layer (E) contains colloidal silica, in the total solid content of the coating layer (E), it is preferably 0.3% by mass to 1.0% by mass, more preferably 0.5% by mass to 0.8% by mass . By setting the content to 0.3% by mass or more, a surface improvement effect can be obtained, and by setting the content to be 1.0% by mass or less, it is possible to more effectively prevent aggregation of the coating layer (E) forming composition.

When colloidal silica is contained in the coating layer (E), it is preferable to use a silane coupling agent in combination from the viewpoint of surface improvement. The silane coupling agent is preferably an alkoxysilane compound, and examples thereof include tetraalkoxysilane, trialkoxysilane, and the like. Among them, a trialkoxysilane is preferred, and an alkoxysilane compound having an amino group is particularly preferred. With respect to the total solid content of the coating layer (E), the addition amount when the silane coupling agent is used in combination is preferably 0.3% by mass to 1.0% by mass, and particularly preferably 0.5% by mass to 0.8% by mass. By setting the addition amount to 0.3% by mass or more, a surface improvement effect can be obtained, and by setting the addition amount to be 1.0% by mass or less, it is possible to more effectively prevent aggregation of the coating layer (E) forming composition.

From the viewpoint of improving weather resistance, it is preferable to add a crosslinking agent to the coating layer (E) to form a crosslinked structure derived from the binder and the crosslinking agent. As the crosslinking agent that can be used for the coating layer (E), the same can be cited as the crosslinking agent that can be used for the primer layer.

As the surfactant used in the coating layer (E), well-known surfactants such as anionic surfactants and nonionic surfactants can be used. When the surfactant is added, the addition amount is preferably 0 mg/m ² to 15 mg/m ² , more preferably 0.5 mg/m ² to 5 mg/m ² . If the addition amount of the surfactant is 0.1 mg/m ² or more, the occurrence of depressions can be suppressed and good layer formation can be obtained. If the addition amount is 15 mg/m ² or less, the adhesion to the adjacent layer is further improved .

-thickness- The thickness of the coating layer (E) is usually preferably 0.5 μm to 12 μm, more preferably 0.5 μm to 5 μm, and still more preferably 0.8 μm to 3 μm. Within the thickness range, weather resistance and durability are further improved, and deterioration of the coating surface shape is suppressed.

The protective sheet for solar cells can also be laminated on the coating layer (E) (outer layer), but from the viewpoint of improving the durability of the protective sheet for solar cells, reducing weight, thickness, and cost, etc. Preferably, the coating layer (E) is the outermost layer of the protective sheet for solar cells.

-Other layers- (Gas barrier layer) A gas barrier layer may be provided on the surface of the substrate opposite to the resin layer (B). The gas barrier layer is a layer that imparts moisture resistance to prevent penetration of water or gas into the base material. As the water vapor transmission rate of gas barrier layer (moisture permeability), preferably from ^{10 2 g / m 2 · day} ~ 10 -6 g / m 2 · day, more preferably from ^{10 1 g / m 2 · day} ~ 10 - ⁵ g / m ² · day, and further more preferably ^{10 0 g / m 2 · day} ~ 10 -4 g / m 2 · day.

As a method of forming a gas barrier layer having such moisture permeability, a dry method is suitable. Examples of the dry method include vacuum vapor deposition methods such as resistance heating vapor deposition, electron beam vapor deposition, induction heating vapor deposition, and auxiliary methods assisted by plasma or ion beams, reactive sputtering methods, Sputtering methods such as ion beam sputtering, ECR (electron cyclotron) sputtering, and physical vapor growth methods such as ion plating (Physical Vapor Deposition (PVD) method), using heat or light, and Plasma and other chemical vapor growth methods (Chemical Vapor Deposition (CVD) method), etc. Among them, a vacuum evaporation method in which a film is formed by an evaporation method under vacuum is preferred.

Examples of the material forming the gas barrier layer include inorganic oxides, inorganic nitrides, inorganic oxynitrides, inorganic halides, and inorganic sulfides. Furthermore, aluminum foil can also be pasted on the substrate as a gas barrier layer.

The thickness of the gas barrier layer is preferably 1 μm or more and 30 μm or less. If the thickness is 1 μm or more, it is difficult for water to penetrate into the substrate during damp and heat (heating) and has excellent hydrolysis resistance. If the thickness is 30 μm or less, the inorganic layer will not become too thick or Due to the stress of the inorganic layer, bumps are generated on the substrate.

＜Solar battery module＞ The solar cell module includes the aforementioned protective sheet for solar cells having a laminated polyester film. The aforementioned protective sheet for solar cells having a laminated polyester film included in the solar cell module has excellent long-term adhesion to the adjacent layer, whereby the solar cell module can maintain stable power generation performance for a long time.

Specifically, the solar cell module includes: a transparent substrate (a front substrate such as a glass substrate) into which sunlight enters; an element structure part, which is provided on the substrate, has solar cell elements and a sealing material for sealing the solar cell elements; And a protective sheet for solar cells, which has a laminated polyester film arranged on the side of the element structure portion opposite to the side where the substrate such as a glass substrate is located; and a transparent front substrate/element structure portion/protective sheet for solar cells laminated layer structure. Specifically, it has the following structure: the element structure part of the solar cell element that converts the light energy of sunlight into electric energy is arranged on the transparent front substrate arranged on the side where sunlight directly enters, and the solar cell Use a sealing material such as ethylene-vinyl acetate copolymer (EVA) between the protective sheet and between the front substrate and the solar cell protective sheet to seal the element structure including the solar cell element (such as the solar cell unit) And then. In particular, the solar cell protective sheet has excellent adhesion to EVA, and can improve long-term durability.

Regarding components other than solar battery modules, solar battery cells, and solar battery protection sheets, for example, "Solar Power Generation System Components" (edited by Eiichi Sugimoto, Kogyo Chosakai Publishing (shares), issued in 2008) There are detailed records in.

The transparent substrate only needs to have translucency that allows sunlight to pass through, and it can be appropriately selected from substrates that allow light to pass through. From the viewpoint of power generation efficiency, the higher the light transmittance, the better. As such a substrate, for example, a glass substrate, a transparent resin substrate such as an acrylic resin, or the like can be suitably used.

As examples of solar cell components, applicable: silicon-based solar cell components such as monocrystalline silicon, polycrystalline silicon, and amorphous silicon, copper-indium-gallium-selenium, copper-indium-selenium, cadmium-tellurium, gallium-arsenic, etc. Various well-known solar cell elements such as group III-V or group II-VI compound semiconductor solar cell elements. The space between the substrate and the solar cell protective sheet can be formed by sealing it with a resin such as an ethylene-vinyl acetate copolymer (a so-called sealing material). [Example]

Hereinafter, an embodiment of the present invention will be specifically explained with examples, but the present invention is not limited to the following examples as long as it does not exceed the gist. In addition, as long as there is no special explanation in advance, "parts" are the quality standards.

-Synthesis of polyester- Add about 123 kg of bis(hydroxyethyl) terephthalate to an esterification reaction tank maintained at a temperature of 250°C and a pressure of 1.2×10 ^{5 Pa.} A slurry of 100 kg of pure terephthalic acid (manufactured by Mitsui Chemicals Co., Ltd.) and 45 kg of ethylene glycol (manufactured by Nippon Shokubai Co., Ltd.). After the supply of high-purity terephthalic acid and ethylene glycol was completed, the esterification reaction further proceeded for 1 hour. After that, 123 kg of the obtained esterification reaction product was transferred to the polycondensation reaction tank.

Then, ethylene glycol was added to the polycondensation reaction tank to which the esterification reaction product was transferred so that it might become 0.3 mass% with respect to the obtained polymer. After stirring for 5 minutes, the ethylene glycol solution of cobalt acetate and the ethylene glycol solution of manganese acetate were added so that the obtained polymer became 30 ppm in terms of cobalt element conversion and 15 ppm in terms of manganese element conversion value. Alcohol solution. After further stirring for 5 minutes, a 2% by mass ethylene glycol solution of the titanium alkoxide compound was added so that the obtained polymer became 5 ppm in terms of titanium element conversion value. After 5 minutes, a 10% by mass ethylene glycol solution of ethyl diethylphosphinoacetate was added so that the obtained polymer became 5 ppm in terms of phosphorus element conversion value. Thereafter, while stirring the oligomer at 30 rpm, the reaction system was gradually heated from 250°C to 285°C, and the pressure in the polycondensation reaction tank was reduced to 40 Pa. The time to reach the final temperature and the final pressure were both set to 60 minutes. The reaction system was flushed with nitrogen at the time when the stirring torque became the prescribed stirring torque, and then returned to normal pressure, and the polycondensation reaction was stopped. Then, the polymer obtained by the polycondensation reaction is sprayed into cold water in a strand shape, and cut immediately to produce polymer particles (about 3 mm in diameter and 7 mm in length). In addition, the time from the start of the pressure reduction until the predetermined stirring torque is reached is 3 hours.

Here, as the titanium alkoxide compound, the titanium alkoxide compound (Ti content=4.44% by mass) synthesized in Example 1 in paragraph [0083] of JP 2005-340616 A was used.

-Solid phase polymerization- In a vacuum vessel maintained at 40 Pa, the particles obtained above were maintained at a temperature of 220° C. for 30 hours to perform solid-phase polymerization.

(Example 1)-Production of laminated polyester film-The pellets after solid phase polymerization as described above were melted at 280°C and then cast on a metal drum to produce unstretched polyterephthalene with a thickness of approximately 3 mm Ethylene formate (PET) film. Thereafter, the unstretched PET film was stretched to 3.4 times in the longitudinal direction (MD) at 90°C, and one side of the uniaxially stretched PET film was subjected to corona discharge treatment under the following conditions. Then, after the MD stretching and before the transverse (TD) stretching, the coating amount became 5.1 mL/m ² , and the composition for forming an undercoat layer with the following composition (composition 1 ) Coated on the corona treated surface of the uniaxially stretched PET film stretched in MD. The PET film coated with the composition for forming an undercoat layer (composition 1) was subjected to TD stretching to form an undercoat layer having a thickness of 0.1 μm and an elastic modulus of 1.5 GPa. In addition, the TD stretching was performed under the conditions of a temperature of 105°C and a stretching ratio of 4.5 times. The PET film with the primer layer is heat-fixed at 190°C on the film surface for 15 seconds, and then at 190°C, the MD relaxation rate is 5% and the TD relaxation rate is 11%, in the MD and TD directions The heat relaxation treatment was performed to obtain a 250 μm-thick biaxially stretched PET film (hereinafter, referred to as "laminated polyester film") with an undercoat layer formed thereon. As a result of measuring the micro-peak temperature of the obtained laminated polyester film by differential scanning calorimetry (DSC), the micro-peak temperature was 185°C.

(Corona discharge treatment) The conditions of the corona discharge treatment performed on one surface of the uniaxially stretched PET film are as follows. ·Interval between electrode and dielectric roller: 1.6 mm ·Processing frequency: 9.6 kHz ·Processing speed: 20 m/min ·Processing intensity: 0.375 kV·A·min/m ²

(Composition of the composition for forming a primer layer (composition 1)) Acrylic resin aqueous dispersion 21.9 copies [AS-563A, manufactured by Daicel Fine Chemicals Co., Ltd., solid content: 28% by mass latex with styrene skeleton] ·Water-soluble oxazoline crosslinking agent 4.9 copies [Epocros (registered trademark) WS-700, manufactured by Nippon Shokubai Co., Ltd., solid content: 25% by mass] ·Fluorine-based surfactants 0.1 copies Distilled water 73.1 copies

On the laminated polyester film obtained in this way, the resin layer (B) and the resin layer (C) were formed as follows.

First, the composition for resin layer (B) formation is prepared so that it may become the composition described below.

-Resin layer (B) forming composition (B1)- Water-soluble oxazoline crosslinking agent 3.3 copies [Epocros (registered trademark) WS-700, manufactured by Nippon Shokubai Co., Ltd., solid content: 25% by mass] Acrylic resin water dispersion 7.4 copies [Bonron (registered trademark) XPS002, manufactured by Mitsui Chemicals Co., Ltd., solid content: 45% by mass, with styrene skeleton in the structure] Colloidal silicon dioxide 10.2 copies [Snowtex (registered trademark) C, manufactured by Nissan Chemical Industry Co., Ltd., solid content: 20% by mass] ·Titanium dioxide dispersion (solid content: 48.0% by mass) 3.3 parts ·Diammonium phosphate (solid content: 35.0 mass%) 0.3 copies ·Fluorine-based surfactants (solid content: 2.0% by mass) 0.3 parts Distilled water 75.3 copies

The "titanium dioxide dispersion" is prepared by the following method. ～Preparation of Titanium Dioxide Dispersion Liquid～ Using a DYNO-MILL disperser, titanium dioxide having a volume average particle diameter of 0.42 μm was dispersed so as to have the following composition to prepare a titanium dioxide dispersion. In addition, the volume average particle size of titanium dioxide was measured using Microtrac FRA manufactured by Honeywell.

～The composition of the titanium dioxide dispersion～ Titanium dioxide 455.8 copies [Tipaque (registered trademark) CR-95, manufactured by Ishihara Sangyo Co., Ltd., powder] ·Polyvinyl alcohol (PVA) aqueous solution 227.9 copies [PVA-105, manufactured by Kuraray Co., Ltd., solid content: 10% by mass] Dispersant 5.5 copies [Demol (registered trademark) EP, manufactured by Kao Corporation, solid content: 25% by mass] Distilled water 310.8 copies

Apply the obtained resin layer (B) forming composition to the surface of the laminated polyester film on the side where the primer layer is formed so that the film thickness after drying (dry film thickness) becomes 0.9 μm, and It dried at 170 degreeC for 2 minutes, and formed the resin layer (B).

Thereafter, a composition for forming a resin layer (C) having the following composition was applied to the surface of the resin layer (B) so that the film thickness after drying became 0.3 μm, and dried to form a resin layer (C) ). The composition of the composition for forming a resin layer (C) is shown below. EMLEX (registered trademark) 110 uses a 2:1 mixed solvent of water/ethanol, diluted to 2% by mass, and used.

-The resin layer (C) forming composition (C1) of Example 1- ·Water-soluble oxazoline crosslinking agent 1.2 copies [Epocros (registered trademark) WS-700, manufactured by Nippon Shokubai Co., Ltd., solid content: 25% by mass] Polyolefin resin aqueous dispersion 9.4 copies [Alowbase (registered trademark) SE-1013N, manufactured by Unigene Co., Ltd., solid content: 20.2% by mass] Acrylic resin aqueous dispersion 1.7 copies [AS-563A, manufactured by Daicel Fine Chemicals Co., Ltd., solid content: 28% by mass latex with styrene skeleton] Surface active agent 4.2 copies [EMALEX (registered trademark) 110, manufactured by Nihon Emulsion (Stock), solid content: 2% by mass] Distilled water 83.4 copies

Furthermore, on the side of the laminated polyester film where the primer layer is not formed, the coating layer (D) forming composition and the coating layer (E) forming composition having the following composition are used to form the coating layer (D) in sequence. ) And the coating layer (E) as a weather-resistant layer to produce a protective sheet for solar cells.

-Formation of coating layer (D)- Preparation of composition for forming coating layer (D) The components described below are mixed to prepare a composition (D1) for forming a coating layer (D). The following "titanium dioxide dispersion" is the same as the titanium dioxide dispersion prepared in the resin layer (B).

-Composition (D1) for forming coating layer (D)- Silicone compounds 381.7 copies [Cerana (Ceranate) (registered trademark) WSA1070, manufactured by DIC, solid content: 38% by mass] Polyoxyalkylene ether 13.1 copies [Naroacty (registered trademark) CL-95, manufactured by Sanyo Chemical Co., Ltd., solid content: 1% by mass] Water-soluble oxazoline crosslinking agent 105.1 copies [Epocros (registered trademark) WS-700, manufactured by Nippon Shokubai Co., Ltd., solid content: 25% by mass] Distilled water 14.3 copies ·Titanium dioxide dispersion (solid content: 48% by mass) 483.4 parts

The coating layer (D) is formed so that the coating amount of the adhesive becomes 4.7 g/m ² and the coating amount of titanium dioxide becomes 5.6 g/m ² , and the obtained composition for forming the coating layer (D) is coated It was spread on the back surface (the non-forming surface of the resin layer (B)) of the laminated polyester film, and dried at 170° C. for 2 minutes to form a coating layer (D) with a film thickness of 20 μm after drying.

-Formation of the coating layer (E)- Apply the coating solution of the composition (E1) for forming the coating layer (E) shown below so that the coating amount of the adhesive becomes 1.3 g/m ² It was spread on the surface of the coating layer (D) and dried at 175°C for 2 minutes to form a coating layer (E) with a thickness of 1 μm.

-Composition (E1) for forming coating layer (E)- Fluorine-based resin 345.0 copies [Obbligato (registered trademark) SW0011F, manufactured by AGC Coat-tech (Stock), solid content: 36% by mass] Colloidal silicon dioxide 3.9 copies [Snowtex (registered trademark) UP, manufactured by Nissan Chemical Industry Co., Ltd., solid content: 20% by mass] Silicone coupler 78.5 copies [TSL8340, Momentive Performance Materials, solid content: 1% by mass]·Synthetic wax 207.0 copies [Chemipearl (registered trademark) W950, manufactured by Mitsui Chemicals Co., Ltd., solid content: 5 mass%] Polyoxyalkylene ether 60.0 copies [Naroacty (registered trademark) CL-95, manufactured by Sanyo Chemical Co., Ltd., solid content: 1% by mass] Carbon diiminium compounds 62.3 copies [Carbodilite (registered trademark) V-02-L2, manufactured by Nisshinbo Chemical Co., Ltd., solid content: 20% by mass] Distilled water 242.8 copies

(Example 2 to Example 17, and Comparative Example 1 to Comparative Example 12) Except that the composition for forming the primer layer, the composition for forming the resin layer (B), the composition for forming the resin layer (C), the minute peak temperature, and the heat-fixing temperature were changed as shown in Table 4, by and In the same manner as in Example 1, Example 2 to Example 17, and Comparative Example 1 to Comparative Example 12 were produced in the same manner. The evaluation shown below was performed for each Example and Comparative Example, and the evaluation result is shown in Table 4. In addition, the details of the composition for forming an undercoat layer, the composition for forming a resin layer (B), and the composition for forming a resin layer (C) are shown in Tables 1 to 3 below.

[Table 1] Raw materials concentration Composition 1 Composition 2 Composition 3 Composition 4 Composition 5 Composition 6 Composition 7 Composition 8 Composition 9 Composition 10 Composition 11 Composition 12 Composition 13 water - 73.1 72.3 71.0 68.9 66.7 64.5 81.3 82.4 74.6 73.1 81.6 78.7 74.6 Epocros WS700 25 4.9 4.9 4.9 4.9 4.9 4.9 4.9 4.9 4.9 4.9 4.9 4.9 4.9 Alowbase SE-1013N 20.2 3.0 7.6 15.2 22.8 30.4 AS-563A 28 21.9 19.7 16.4 10.9 5.5 Bonron XPS002 45 13.7 Joncryl PDX-7341 49 12.6 Hardlen NZ-1001 30 20.4 Hytec S3148 28 21.9 Superflex 500M 46 13.4 Superflex 460S 37.6 16.3 Finetex ES2200 30 20.4 Fluorine-based surfactant 2 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 total 100 100 100 100 100 100 100 100 100 100 100 100 100

The description in Table 1 will be described. Joncryl (registered trademark) PDX-7341: acrylic resin, manufactured by BASF Hardlen (registered trademark) NZ-1001: polyolefin resin, manufactured by Toyobo Co., Ltd. Hytec S3148: Polyolefin resin, manufactured by Toho Chemical Industry Co., Ltd. Superflex (registered trademark) 500M: Polyurethane resin, manufactured by Daiichi Industrial Pharmaceutical Co., Ltd. Superflex (registered trademark) 460S: polyurethane resin, manufactured by Daiichi Industrial Pharmaceutical Co., Ltd. Finetex (registered trademark) ES2200: polyester resin, manufactured by DIC

[Table 2] Raw materials concentration B1 B2 water - 75.3 7.4 Snowtex C 20.0 10.2 - Titanium oxide dispersion 49.0 3.3 30.5 Epocros WS700 25.0 3.3 12.5 Diammonium Phosphate 35.0 0.3 0.8 Bonron S002 45.0 7.4 - Alowbase SE-1013N 20.2 - 40.6 AS-563A 28.0 - 7.8 Fluorine-based surfactant 2.0 0.3 0.4 total 100.0 100.0

[table 3] Raw materials concentration C1 C2 water - 83.4 73.7 Epocros WS700 25.0 1.2 4.3 Alowbase SE-1013N 20.2 9.4 19.8 AS-563A 28.0 1.7 0.9 EMALEX 110 10.0 4.2 - Naroacty CL-95 1.0 - 1.0 Fluorine-based surfactant 2.0 - 0.2 total 100.0 100.0

(Resistant to agglomeration and destruction) The resistance to agglomeration destruction was evaluated by the following method. The solar cell protective sheet obtained in each example was cut into 1.0 cm (TD direction)×30 cm (MD direction). Then, two EVA films (Hangzhou, F806) were laminated on a glass plate of 20 cm×20 cm×thickness 0.3 cm. A polyethylene terephthalate (PET) film treated with a release agent (Cerapeel ) (Registered trademark), manufactured by Toray (Co., Ltd.), the other end is combined with the end of the MD of the solar cell protective sheet, and the resin layer (C) is attached to the EVA film The protective sheet for solar cells is then vacuumized at 145°C for 4 minutes and pressurized for 10 minutes using a vacuum laminating device (LAMINATOR) 0505S manufactured by Nisshinbo Mechatronics (Co., Ltd.) ) Laminate to make samples. Under the conditions of a temperature of 23°C and a relative humidity of 50%, the solar cell protective sheet attached to the EVA is humidity-conditioned for more than 24 hours, and then a tensile testing machine (Teng Xilong (Teng Xilong ( Tensilon): manufactured by A&D Company), a tensile test was performed on the 1.0 cm wide part of the sample prepared above at a peeling angle of 180°. In addition, the fracture stress was evaluated based on the following evaluation criteria. The higher the breaking stress, the better the evaluation is that the resistance to cohesive destruction is.

-Evaluation criteria- 5: The stress at the top of the peak is 9 N/mm or more. 4: The stress at the top of the peak is 8 N/mm or more but less than 9 N/mm. 3: The stress at the top of the peak is 6 N/mm or more but less than 8 N/mm. 2: The stress at the top of the peak is 4 N/mm or more but less than 6 N/mm. 1: The stress at the top of the peak is 0 N/mm or more and less than 4 N/mm.

(Weather resistance) The retention half-life of elongation at break was measured by the following method, and the weather resistance (humid heat stability) was evaluated based on the following criteria. -Retention half-life of elongation at break- Under the conditions of 120°C and 100% relative humidity, the obtained laminated polyester film was stored (heated), and the elongation at break (%) relative to the laminated polyester film before the storage treatment was measured, The elongation at break (%) of the laminated polyester film after the storage treatment becomes 50% of the storage time (the half-life of the retention of the elongation at break). The longer the retention half-life of the elongation at break, the better the moisture-heat stability of the laminated polyester film.

-Evaluation criteria- 5: The elongation at break half-life time is 100 hours or more. 4: The elongation at break half-life time is 90 hours or more but less than 100 hours. 3: The elongation at break half-life time is 80 hours or more but less than 90 hours. 2: The elongation at break half-life time is 70 hours or more but less than 80 hours. 1: The elongation at break half-life time is less than 70 hours.

[Table 4] Undercoat Resin layer (B) Resin layer (C) Coating layer (D) Coating layer (E) Biaxial stretch film Heat fixation temperature Evaluation results Composition Resin type Allocation ratio Dry film thickness Elasticity Composition Dry film thickness Composition Dry film thickness Composition Dry film thickness Composition Dry film thickness Small peak temperature set temperature Resistance to agglomeration and destruction Weather resistance (Quality ratio) (Μm) (GPa) (Μm) (Μm) (Μm) (Μm) (℃) (℃) Example 1 Composition 1 Acrylic 100 0.1 1.5 B1 0.9 C1 0.3 D1 20 E1 1 185 190 5 5 Example 2 Composition 2 Acrylic olefin series 90 10 0.1 1.3 B1 0.9 C1 0.3 D1 20 E1 1 185 190 4 5 Example 3 Composition 3 Acrylic olefin series 75 25 0.1 1.1 B1 0.9 C1 0.3 D1 20 E1 1 185 190 4 5 Example 4 Composition 4 Acrylic olefin series 50 50 0.1 0.8 B1 0.9 C1 0.3 D1 20 E1 1 185 190 3 5 Comparative example 1 Composition 5 Acrylic olefin series 25 75 0.1 0.2 B1 0.9 C1 0.3 D1 20 E1 1 185 190 2 5 Comparative example 2 Composition 6 Olefins 100 0.1 0.1 B1 0.9 C1 0.3 D1 20 E1 1 185 190 1 5 Comparative example 3 Composition 7 Acrylic 100 0.1 0.6 B1 0.9 C1 0.3 D1 20 E1 1 185 190 1 5 Comparative example 4 Composition 8 Acrylic 100 0.1 0.1 B1 0.9 C1 0.3 D1 20 E1 1 185 190 1 5 Comparative example 5 Composition 9 Olefins 100 0.1 0.6 B1 0.9 C1 0.3 D1 20 E1 1 185 190 1 5 Comparative example 6 Composition 10 Olefins 100 0.1 0.1 B1 0.9 C1 0.3 D1 20 E1 1 185 190 1 5 Comparative example 7 Composition 11 Polyurethane series 100 0.1 0.1 B1 0.9 C1 0.3 D1 20 E1 1 185 190 1 5 Comparative example 8 Composition 12 Polyurethane series 100 0.1 0.2 B1 0.9 C1 0.3 D1 20 E1 1 185 190 1 5 Example 5 Composition 13 Polyester series 100 0.1 1.4 B1 0.9 C1 0.3 D1 20 E1 1 185 190 3 5 Comparative example 9 Composition 1 Acrylic 100 0.1 1.5 B1 0.9 C1 0.3 D1 20 E1 1 220 225 5 2 Example 6 Composition 1 Acrylic 100 0.1 1.5 B1 0.9 C1 0.3 D1 20 E1 1 210 215 5 3 Example 7 Composition 1 Acrylic 100 0.1 1.5 B1 0.9 C1 0.3 D1 20 E1 1 200 205 5 4 Example 8 Composition 1 Acrylic 100 0.1 1.5 B1 0.9 C1 0.3 D1 20 E1 1 190 195 5 5 Example 9 Composition 1 Acrylic 100 0.1 1.5 B1 0.9 C1 0.3 D1 20 E1 1 180 185 5 5 Example 10 Composition 1 Acrylic 100 0.1 1.5 B1 0.9 C1 0.3 D1 20 E1 1 170 175 5 4 Example 11 Composition 1 Acrylic 100 0.1 1.5 B1 0.9 C1 0.3 D1 20 E1 1 160 165 3 3 Comparative example 10 Composition 1 Acrylic 100 0.1 1.5 B1 0.9 C1 0.3 D1 20 E1 1 150 155 1 2 Comparative example 11 Composition 1 Acrylic 100 0.1 1.5 B2 6.5 C2 0.5 D1 20 E1 1 220 225 5 2 Example 12 Composition 1 Acrylic 100 0.1 1.5 B2 6.5 C2 0.5 D1 20 E1 1 210 215 5 3 Example 13 Composition 1 Acrylic 100 0.1 1.5 B2 6.5 C2 0.5 D1 20 E1 1 200 205 5 4 Example 14 Composition 1 Acrylic 100 0.1 1.5 B2 6.5 C2 0.5 D1 20 E1 1 190 195 5 5 Example 15 Composition 1 Acrylic 100 0.1 1.5 B2 6.5 C2 0.5 D1 20 E1 1 180 185 5 5 Example 16 Composition 1 Acrylic 100 0.1 1.5 B2 6.5 C2 0.5 D1 20 E1 1 170 175 5 4 Example 17 Composition 1 Acrylic 100 0.1 1.5 B2 6.5 C2 0.5 D1 20 E1 1 160 165 2 3 Comparative example 12 Composition 1 Acrylic 100 0.1 1.5 B2 6.5 C2 0.5 D1 20 E1 1 150 155 1 2

(Example 18 to Example 34) ＜Production of solar cell module＞ Using the protective sheets for solar cells of Examples 1 to 17, the solar cell modules of Examples 18 to 34 were produced by the following method.

Tempered glass (transparent base material) with a thickness of 3.2 mm, EVA sheet (sealing material) (SC50B manufactured by Mitsui Chemicals Fabro (Co., Ltd.)), crystalline solar cell unit (solar cell element) ), EVA sheet (SC50B manufactured by Mitsui Chemicals Fabro (Co., Ltd.)), and any one of the protective sheets for solar cells of Examples 1 to 17 are stacked in sequence, and a vacuum laminator is used (Manufactured by Nisshinbo Precision Machinery Co., Ltd., vacuum laminator) heat presses to bond each component to the EVA sheet. In the manner described, a solar cell module is produced.

(Evaluation) As a result of a power generation operation test on each of the solar cell modules of Examples 18 to 34 produced above, in any of the examples, good power generation performance was shown as a solar cell.

The entire content of the disclosure of Japanese Patent Application No. 2014-156943 can be incorporated into this specification by reference. All documents, patent applications, and technical specifications described in this specification are incorporated into this specification by reference to the same degree as the following cases, which are specifically and individually described and incorporated into each by reference Documents, patent applications, and technical specifications.

none

Claims (12)

A laminated polyester film, which comprises: A biaxially stretched polyester film is produced by extending an unstretched polyester film in the first direction and extending along the surface of the film in a second direction orthogonal to the first direction. The minute peak temperature derived from the heat fixation temperature measured by differential scanning calorimetry is 170°C or more and 200°C or less; and The primer layer is formed by applying the primer layer forming composition to one surface of the polyester film stretched in the first direction before extending in the second direction, and then It is formed by stretching in the second direction, and the modulus of elasticity at 23.0°C is 1.0 GPa or more and 1.5 GPa or less, The primer layer contains acrylic resin, The acrylic resin contained in the undercoat layer has a styrene skeleton. The laminated polyester film according to claim 1, wherein the primer layer contains an acrylic resin, and the content ratio of the acrylic resin in the resin component contained in the primer layer is 50% by mass or more. The laminated polyester film according to claim 2, wherein the content ratio of the acrylic resin in the resin component contained in the undercoat layer is 75% by mass or more. The laminated polyester film according to claim 1 or claim 2, wherein the elastic modulus at 23.0°C of the primer layer is 1.3 GPa or more and 1.5 GPa or less. The laminated polyester film according to claim 1 or 2, wherein the minute peak temperature of the biaxially stretched polyester film is 180°C or more and 190°C or less. The laminated polyester film according to claim 1 or 2, wherein the undercoat layer further contains an oxazoline-based crosslinking agent. A protective sheet for solar cells, comprising: the laminated polyester film according to any one of claims 1 to 6, and an acrylic resin-containing resin layer disposed on the undercoat layer of the laminated polyester film Resin layer. The protective sheet for a solar cell according to claim 7, wherein the resin layer has a structure in which at least two layers are laminated, and the outermost layer farthest from the laminated polyester film contains acrylic resin and polyolefin resin. The solar cell protective sheet according to claim 7 or claim 8, wherein the laminated polyester film has a weather-resistant layer on the side opposite to the side having the primer layer. The protective sheet for a solar cell according to claim 9, wherein the weather-resistant layer has a structure in which at least two layers are laminated, and the weather-resistant layer furthest from the laminated polyester film contains a fluorine-based polymer. A solar cell module comprising the protective sheet for solar cells according to any one of claim 7 to claim 10. A manufacturing method of laminated polyester film, which includes: The step of stretching the unstretched polyester film in the first direction; The step of applying a composition for forming an undercoat layer to one surface of a polyester film stretched in the first direction, the composition for forming an undercoat layer containing an acrylic resin; The polyester film coated with the composition for forming a primer layer was stretched along the film surface in a second direction orthogonal to the first direction, and the elastic modulus at 23.0°C was 1.0 GPa Steps for the primer coating above and below 1.5 GPa; and A heat-fixing step of heat-fixing the polyester film formed with the primer layer at 165°C or higher and 215°C or lower; and A biaxially stretched polyester film formed with the primer layer was produced.